Methods and apparatus for generating and modulating illumination conditions

ABSTRACT

A lighting fixture for producing a beam of light having a prescribed luminous flux spectrum. In one example, the lighting fixture comprises a plurality of groups of light-emitting devices, each such group configured to emit light having a distinct luminous flux spectrum, and a controller configurable to supply selected amounts of electrical power to the plurality of groups of light-emitting devices, such that the groups cooperate to produce a composite beam of light having a prescribed luminous flux spectrum.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 120 as acontinuation of U.S. Non-provisional application Ser. No. 09/716,819,filed Nov. 20, 2000, entitled “Systems and Methods for Generating andModulating Illumination Conditions,” which in turn claims priority toeach of the following U.S. Provisional Applications:

-   -   Serial No. 60/166,533, filed Nov. 18, 1999, entitled “Designing        Lights with LED Spectrum;”    -   Serial No. 60/201,140, filed May 2, 2000, entitled “Systems and        Methods for Modulating Illumination Conditions;” and    -   Serial No. 60/235,678, filed Sep. 27, 2000, entitled        “Ultraviolet Light Emitting Diode Device.”

Each of the above references is hereby incorporated herein by reference.

BACKGROUND

Human beings have grown accustomed to controlling their environment.Nature is unpredictable and often presents conditions that are far froma human being's ideal living conditions. The human race has thereforetried for years to engineer the environment inside a structure toemulate the outside environment at a perfect set of conditions. This hasinvolved temperature control, air quality control and lighting control.

The desire to control the properties of light in an artificialenvironment is easy to understand. Humans are primarily visual creatureswith much of our communication being done visually. We can identifyfriends and loved ones based on primarily visual cues and we communicatethrough many visual mediums, such as this printed page. At the sametime, the human eye requires light to see by and our eyes (unlike thoseof some other creatures) are particularly sensitive to color.

With today's ever-increasing work hours and time constraints, less andless of the day is being spent by the average human outside in naturalsunlight. In addition, humans spend about a third of their lives asleep,and as the economy increases to 24/7/365, many employees no longer havethe luxury of spending their waking hours during daylight. Therefore,most of an average human's life is spent inside, illuminated by manmadesources of light.

Visible light is a collection of electromagnetic waves (electromagneticradiation) of different frequencies, each wavelength of which representsa particular “color” of the light spectrum. Visible light is generallythought to comprise those light waves with wavelength between about 400nm and about 700 nm. Each of the wavelengths within this spectrumcomprises a distinct color of light from deep blue/purple at around 400nm to dark red at around 700 nm. Mixing these colors of light producesadditional colors of light. The distinctive color of a neon sign resultsfrom a number of discrete wavelengths of light. These wavelengthscombine additively to produce the resulting wave or spectrum that makesup a color. One such color is white light.

Because of the importance of white light, and since white light is themixing of multiple wavelengths of light, there have arisen multipletechniques for characterization of white light that relate to how humanbeings interpret a particular white light. The first of these is the useof color temperature, which relates to the color of the light withinwhite. Correlated color temperature is characterized in colorreproduction fields according to the temperature in degrees Kelvin (K)of a black body radiator that radiates the same color light as the lightin question. FIG. 1 is a chromaticity diagram in which Planckian locus(or black body locus or white line) (104) gives the temperatures ofwhites from about 700 K (generally considered the first visible to thehuman eye) to essentially the terminal point. The color temperature ofviewing light depends on the color content of the viewing light as shownby line (104). Thus, early morning daylight has a color temperature ofabout 3,000 K while overcast midday skies have a white color temperatureof about 10,000 K. A fire has a color temperature of about 1,800 K andan incandescent bulb about 2848 K. A color image viewed at 3,000 K willhave a relatively reddish tone, whereas the same color image viewed at10,000 K will have a relatively bluish tone. All of this light is called“white,” but it has varying spectral content.

The second classification of white light involves its quality. In 1965the Commission Internationale de l'Eclairage (CIE) recommended a methodfor measuring the color rendering properties of light sources based on atest color sample method. This method has been updated and is describedin the CIE 13.3-1995 technical report “Method of Measuring andSpecifying Colour Rendering Properties of Light Sources,” the disclosureof which is herein incorporated by reference. In essence, this methodinvolves the spectroradiometric measurement of the light source undertest. This data is multiplied by the reflectance spectrums of eightcolor samples. The resulting spectrums are converted to tristimulusvalues based on the CIE 1931 standard observer. The shift of thesevalues with respect to a reference light are determined for the uniformcolor space (UCS) recommended in 1960 by the CIE. The average of theeight color shifts is calculated to generate the General Color RenderingIndex, known as CRI. Within these calculations the CRI is scaled so thata perfect score equals 100, where perfect would be using a sourcespectrally equal to the reference source (often sunlight or fillspectrum white light). For example a tungsten-halogen source compared tofull spectrum white light might have a CPU of 99 while a warm whitefluorescent lamp would have a CRI of 50.

Artificial lighting generally uses the standard CRI to determine thequality of white light. If a light yields a high CRI compared to fullspectrum white light then it is considered to generate better qualitywhite light (light that is more “natural” and enables colored surfacesto be better rendered). This method has been used since 1965 as a pointof comparison for all different types of light sources.

In addition to white light, the ability to generate specific colors oflight is also highly sought after. Because of humans' light sensitivity,visual arts and similar professions desire colored light that isspecifiable and reproducible. Elementary film study classes teach that amovie-goer has been trained that light which is generally more orange orred signifies the morning, while light that is generally more bluesignifies a night or evening. We have also been trained that sunlightfiltered through water has a certain color, while sunlight filteredthrough glass has a different color. For all these reasons it isdesirable for those involved in visual arts to be able to produce exactcolors of light, and to be able to reproduce them later.

Current lighting technology makes such adjustment and control difficult,because common sources of light, such as halogen, incandescent, andfluorescent sources, generate light of a fixed color temperature andspectrum. Further, altering the color temperature or spectrum willusually alter other lighting variables in an undesirable way. Forexample, increasing the voltage applied to an incandescent light mayraise the color temperature of the resulting light, but also results inan overall increase in brightness. In the same way, placing a deep bluefilter in front of a white halogen lamp will dramatically decrease theoverall brightness of the light. The filter itself will also get quitehot (and potentially melt) as it absorbs a large percentage of the lightenergy from the white light.

Moreover, achieving certain color conditions with incandescent sourcescan be difficult or impossible as the desired color may cause thefilament to rapidly burn out. For fluorescent lighting sources, thecolor temperature is controlled by the composition of the phosphor,which may vary from bulb to bulb but cannot typically be altered for agiven bulb. Thus, modulating color temperature of light is a complexprocedure that is often avoided in scenarios where such adjustment maybe beneficial.

In artificial lighting, control over the range of colors that can beproduced by a lighting fixture is desirable. Many lighting fixturesknown in the art can only produce a single color of light instead ofrange of colors. That color may vary across lighting fixtures (forinstance a fluorescent lighting fixture produces a different color oflight than a sodium vapor lamp). The use of filters on a lightingfixture does not enable a lighting fixture to produce a range of colors,it merely allows a lighting fixture to produce its single color, whichis then partially absorbed and partially transmitted by the filter. Oncethe filter is placed, the fixture can only produce a single (nowdifferent) color of light, but cannot produce a range of colors.

In control of artificial lighting, it is further desirable to be able tospecify a point within the range of color producible by a lightingfixture that will be the point of highest intensity. Even on currenttechnology lighting fixtures whose colors can be altered, the point ofmaximum intensity cannot be specified by the user, but is usuallydetermined by unalterable physical characteristics of the fixture. Thus,an incandescent light fixture can produce a range of colors, but theintensity necessarily increases as the color temperature increases whichdoes not enable control of the color at the point of maximum intensity.Filters further lack control of the point of maximum intensity, as thepoint of maximum intensity of a lighting fixture will be the unfilteredcolor (any filter absorbs some of the intensity).

SUMMARY

Applicants have appreciated that the correlated color temperature, andCRI, of viewing light can affect the way in which an observer perceivesa color image. An observer will perceive the same color imagedifferently when viewed under lights having different correlated colortemperatures. For example, a color image which looks normal when viewedin early morning daylight will look bluish and washed out when viewedunder overcast midday skies. Further, a white light with a poor CRI maycause colored surfaces to appear distorted.

Applicants also have appreciated that the color temperature and/or CRIof light is critical to creators of images, such as photographers, filmand television producers, painters, etc., as well as to the viewers ofpaintings, photographs, and other such images. Ideally, both creator andviewer utilize the same color of ambient light, ensuring that theappearance of the image to the viewer matches that of the creator.

Applicants have further appreciated that the color temperature ofambient light affects how viewers perceive a display, such as a retailor marketing display, by changing the perceived color of such items asfruits and vegetables, clothing, furniture, automobiles, and otherproducts containing visual elements that can greatly affect how peopleview and react to such displays. One example is a tenet of theatricallighting design that strong green light on the human body (even if theoverall lighting effect is white light) tends to make the human lookunnatural, creepy, and often a little disgusting. Thus, variations inthe color temperature of lighting can affect how appealing or attractivesuch a display may be to customers.

Moreover, the ability to view a decoratively colored item, such asfabric-covered furniture, clothing, paint, wallpaper, curtains, etc., ina lighting environment or color temperature condition which matches orclosely approximates the conditions under which the item will be viewedwould permit such colored items to be more accurately matched andcoordinated. Typically, the lighting used in a display setting, such asa showroom, cannot be varied and is often chosen to highlight aparticular facet of the color of the item leaving a purchaser to guessas to whether the item in question will retain an attractive appearanceunder the lighting conditions where the item will eventually be placed.Differences in lighting can also leave a customer wondering whether thecolor of the item will clash with other items that cannot convenientlybe viewed under identical lighting conditions or otherwise directlycompared.

In view of the foregoing, one embodiment of the present inventionrelates to systems and methods for generating and/or modulatingillumination conditions to generate light of a desired and controllablecolor, for creating lighting fixtures for producing light in desirableand reproducible colors, and for modifying the color temperature orcolor shade of light produced by a lighting fixture within aprespecified range after a lighting fixture is constructed. In oneembodiment, LED lighting units capable of generating light of a range ofcolors are used to provide light or supplement ambient light to affordlighting conditions suitable for a wide range of applications.

Disclosed is a first embodiment which comprises a lighting fixture forgenerating white light including a plurality of component illuminationsources (such as LEDs), producing electromagnetic radiation of at leasttwo different spectrums (including embodiments with exactly two orexactly three), each of the spectrums having a maximum spectral peakoutside the region 510 nm to 570 nm, the illumination sources mounted ona mounting allowing the spectrums to mix so that the resulting spectrumis substantially continuous in the photopic response of the human eyeand/or in the wavelengths from 400 nm to 700 nm.

In another embodiment, the lighting fixture can include illuminationsources that are not LEDs possibly with a maximum spectral peak withinthe region 510 nm to 570 nm. In yet another embodiment, the fixture canproduce white light within a range of color temperatures such as, butnot limited to, the range 500K to 10,000K and the range 2300 K to 4500K. The specific color or color temperature in the range may becontrolled by a controller. In an embodiment the fixture contains afilter on at least one of the illumination sources which may beselected, possibly from a range of filters, to allow the fixture toproduce a particular range of colors. The lighting fixture may alsoinclude in one embodiment illumination sources with wavelengths outsidethe above discussed 400 nm to 700 nm range.

In another embodiment, the lighting fixture can comprise a plurality ofLEDs producing three spectrums of electromagnetic radiation with maximumspectral peaks outside the region of 530 nm, to 570 nm (such as 450 nmand/or 592 nm) where the additive interference of the spectrums resultsin white light. The lighting fixture may produce white light within arange of color temperatures such as, but not limited to, the range 500Kto 10,000K and the range 2300K to 4500 K. The lighting fixture mayinclude a controller and/or a processor for controlling the intensitiesof the LEDs to produce various color temperatures in the range.

Another embodiment comprises a lighting fixture to be used in a lampdesigned to take fluorescent tubes, the lighting fixture having at leastone component illumination source (often two or more) such as LEDsmounted on a mounting, and having a connector on the mounting that cancouple to a fluorescent lamp and receive power from the lamp. It alsocontains a control or electrical circuit to enable the ballast voltageof the lamp to be used to power or control the LEDs. This controlcircuit could include a processor, and/or could control the illuminationprovided by the fixture based on the power provided to the lamp. Thelighting fixture, in one embodiment, is contained in a housing, thehousing could be generally cylindrical in shape, could contain a filter,and/or could be partially transparent or translucent. The fixture couldproduce white, or other colored, light.

Another embodiment comprises a lighting fixture for generating whitelight including a plurality of component illumination sources (such asLEDs, illumination devices containing a phosphor, or LEDs containing aphosphor), including component illumination sources producing spectrumsof electromagnetic radiation. The component illumination sources aremounted on a mounting designed to allow the spectrums to mix and form aresulting spectrum, wherein the resulting spectrum has intensity greaterthan background noise at its lowest spectral valley. The lowest spectralvalley within the visible range can also have an intensity of at least5%, 10%, 25%, 50% or 75% of the intensity of its maximum spectral peak.The lighting fixture may be able to generate white light at a range ofcolor temperatures and may include a controller and/or processor forenabling the selection of a particular color or color temperature inthat range.

Another embodiment of a lighting fixture could include a plurality ofcomponent illumination sources (such as LEDs), the componentillumination sources producing electromagnetic radiation of at least twodifferent spectrums, the illumination sources being mounted on amounting designed to allow the spectrums to mix and form a resultingspectrum, wherein the resulting spectrum does not have a spectral valleyat a longer wavelength than the maximum spectral peak within thephotopic response of the human eye and/or in the area from 400 nm to 700nm.

Another embodiment comprises a method for generating white lightincluding the steps of mounting a plurality of component illuminationsources producing electromagnetic radiation of at least two differentspectrums in such a way as to mix the spectrums; and choosing thespectrums in such a way that the mix of the spectrums has intensitygreater than background noise at its lowest spectral valley.

Another embodiment comprises a system for controlling illuminationconditions including, a lighting fixture for providing illumination ofany of a range of colors, the lighting fixture being constructed of aplurality of component illumination sources (such as LEDs and/orpotentially of three different colors), a processor coupled to thelighting fixture for controlling the lighting fixture, and a controllercoupled to the processor for specifying illumination conditions to beprovided by the lighting fixture. The controller could be computerhardware or computer software; a sensor such as, but not limited to aphotodiode, a radiometer, a photometer, a colorimeter, a spectralradiometer, a camera; or a manual interface such as, but not limited to,a slider, a dial, a joystick, a trackpad, or a trackball. The processorcould include a memory (such as a database) of predetermined colorconditions and/or an interface-providing mechanism for providing a userinterface potentially including a color spectrum, a color temperaturespectrum, or a chromaticity diagram.

In another embodiment the system could include a second source ofillumination such an, but not limited to, a fluorescent bulb, anincandescent bulb, a mercury vapor lamp, a sodium vapor lamp, an arcdischarge lamp, sunlight, moonlight, candlelight, an LED display system,an LED, or a lighting system controlled by pulse width modulation. Thesecond source could be used by the controller to specify illuminationconditions for the lighting fixture based on the illumination of thelighting fixture and the second source illumination and/or the combinedlight from the lighting fixture and the second source could be a desiredcolor temperature.

Another embodiment comprises a method with steps including generatinglight having color and brightness using a lighting fixture capable ofgenerating light of any range of colors, measuring illuminationconditions, and modulating the color or brightness of the generatedlight to achieve a target illumination condition. The measuring ofillumination conditions could include detecting color characteristics ofthe illumination conditions using a light sensor such as, but notlimited to, a photodiode, a radiometer, a photometer, a calorimeter, aspectral radiometer, or a camera; visually evaluating illuminationconditions, and modulating the color or brightness of the generatedlight includes varying the color or brightness of the generated lightusing a manual interface; or measuring illumination conditions includingdetecting color characteristics of the illumination conditions using alight sensor, and modulating the color or brightness of the generatedlight including varying the color or brightness of the generated lightusing a processor until color characteristics of the illuminationconditions detected by the light sensor match color characteristics ofthe target illumination conditions. The method could include selecting atarget illumination condition such as, but not limited to, selecting atarget color temperature and/or providing an interface comprising adepiction of a color range and selecting a color within the color range.The method could also have steps for providing a second source ofillumination, such as, but not limited to, a fluorescent bulb, anincandescent bulb, a mercury vapor lamp, a sodium vapor lamp, an arcdischarge lamp, sunlight, moonlight, candlelight, an LED lightingsystem, an LED, or a lighting system controlled by pulse widthmodulation. The method could measure illumination conditions includingdetecting light generated by the lighting fixture and by the secondsource of illumination.

In another embodiment modulating the color or brightness of thegenerated light includes varying the illumination conditions to achievea target color temperature or the lighting fixture could comprise one ofa plurality of lighting fixtures, capable of generating a range ofcolors.

In yet another embodiment there is a method for designing a lightingfixture comprising, selecting a desired range of colors to be producedby the lighting fixture, choosing a selected color of light to beproduced by the lighting fixture when the lighting fixture is at maximumintensity, and designing the lighting fixture from a plurality ofillumination sources (such as LEDs) such that the lighting fixture canproduce the range of colors, and produces the selected color when atmaximum intensity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chromaticity diagram including the black body locus;

FIG. 2 depicts an embodiment of a lighting fixture suitable for use inthis invention;

FIG. 3 depicts the use of multiple lighting fixtures according to oneembodiment of the invention;

FIG. 4 depicts an embodiment of a housing for use in one embodiment ofthis invention;

FIGS. 5 a and 5 b depict another embodiment of a housing for use in oneembodiment of this invention;

FIG. 6 depicts an embodiment of a computer interface enabling a user todesign a lighting fixture capable of producing a desired spectrum;

FIG. 7 shows an embodiment for calibrating or controlling the lightfixture of the invention using a sensor;

FIG. 8 a shows a general embodiment of the control of a lighting fixtureof this invention;

FIG. 8 b shows one embodiment of the control of a lighting fixtureinvention in conjunction with a second source of light;

FIG. 9 shows an embodiment for controlling a light fixture of theinvention using a computer interface;

FIG. 10 a shows another embodiment for controlling a lighting fixture ofthis invention using a manual control;

FIG. 10 b depicts a close up of a control unit such as the one used inFIG. 10 a;

FIG. 11 shows an embodiment of a control system which enables multiplelighting control to simulate an environment;

FIG. 12 depicts the CIE spectral luminosity function Vλ which indicatesthe receptivity of the human eye;

FIG. 13 depicts spectral distributions of black body sources at 5,000 Kand 2,500 K;

FIG. 14 depicts one embodiment of a nine LED white light source;

FIG. 15 a depicts the output of one embodiment of a lighting fixturecomprising nine LEDs and producing 5,000 K white light;

FIG. 15 b depicts the output of one embodiment of a lighting fixturecomprising nine LEDs and producing 2,500 K white light;

FIG. 16 depicts one embodiment of the component spectrums of a three LEDlight fixture;

FIG. 17 a depicts the output of one embodiment of a lighting fixturecomprising three LEDs and producing 5,000 K white light;

FIG. 17 b depicts the output of one embodiment of a lighting fixturecomprising three LEDs and producing 2,500 K white light;

FIG. 18 depicts the spectrum of a white Nichia LED, NSP510 BS (bin A);

FIG. 19 depicts the spectrum of a white Nichia LED, NSP510 BS (bin C);

FIG. 20 depicts the spectral transmission of one embodiment of a highpass filter;

FIG. 21 a depicts the spectrum of FIG. 18 and the shifted spectrum frompassing the spectrum of FIG. 18 through the high pass filter in FIG. 20;

FIG. 21 b depicts the spectrum of FIG. 19 and the shifted spectrum frompassing the spectrum of FIG. 19 through the high pass filter in FIG. 20;

FIG. 22 is a chromaticity map showing the black body locus (white line)enlarged on a portion of temperature between 2,300K and 4,500K. Alsoshown is the light produced by two LEDs in one embodiment of theinvention;

FIG. 23 is the chromaticity map further showing the gamut of lightproduced by three LEDs in one embodiment of the invention;

FIG. 24 shows a graphical comparison of the CRI of a lighting fixture ofthe invention compared to existing white light sources;

FIG. 25 shows the luminous output of a lighting fixture of the inventionat various color temperatures;

FIG. 26 a depicts the spectrum of one embodiment of a white lightfixture according to the invention producing light at 2300K;

FIG. 26 b depicts the spectrum of one embodiment of a white lightfixture producing light at 4500K;

FIG. 27 is a diagram of the spectrum of a compact fluorescent lightfixture with the spectral luminosity function as a dotted line;

FIG. 28 shows a lamp for using fluorescent tubes as is known in the art;

FIG. 29 depicts one possible LED lighting fixture which could be used toreplace a fluorescent tube; and

FIG. 30 depicts one embodiment of how a series of filters could be usedto enclose different portions of the black body locus.

DETAILED DESCRIPTION

The description below pertains to several illustrative embodiments ofthe invention. Although many variations of the invention may beenvisioned by one skilled in the art, such variations and improvementsare intended to fall within the scope of this disclosure. Thus, thescope of the invention is not to be unduly limited in any way by thedisclosure below.

As used in this document, the following terms generally have thefollowing meanings; however, these definitions are in no way intended tolimit the scope of the term as would be understood by one of skill inthe art.

As used herein, the term “LED system” means any electroluminescent diodeor other type of carrier injection/junction-based system that is capableof receiving an electrical signal and producing radiation in response tothe signal. Thus, the term “LED” generally includes light emittingdiodes of all types and also includes, but is not limited to, lightemitting polymers, semiconductor dies that produce light in response toa current, organic LEDs, electron luminescent strips, super luminescentdiodes (SLDs) and other such devices. In an embodiment, an “LED” mayrefer to a single light emitting diode having multiple semiconductordies that are individually controlled. The term LEDs does not restrictthe physical or electrical packaging of any of the above and thatpackaging could include, but is not limited to, surface mount,chip-on-board, or T-package mount LEDs and LEDs of all otherconfigurations. The term “LED” also includes LEDs packaged or associatedwith material (e.g. a phosphor) wherein the material may convert energyfrom the LED to a different wavelength. For example, the term “LED” alsoincludes constructions that include a phosphor where the LED emissionpumps the phosphor and the phosphor converts the energy to longerwavelength energy. White LEDs typically use an LED chip that producesshort wavelength radiation and the phosphor is used to convert theenergy to longer wavelengths. This construction also typically resultsin broadband radiation as compared to the original chip radiation.

“Illumination source” includes all illumination sources, including, butnot limited to, LEDs; incandescent sources including filament lamps;pyro-luminescent sources such as flames; candle-luminescent sources suchas gas mantles and carbon arc radiation sources; photo-luminescentsources including gaseous discharges; fluorescent sources;phosphorescence sources; lasers; electro-luminescent sources such aselectro-luminescent lamps; cathode luminescent sources using electronicsatiation; and miscellaneous luminescent sources includinggalvano-luminescent sources, crystallo-luminescent sources,kine-luminescent sources, thermo-luminescent sources, tribo-luminescentsources, sono-luminescent sources, and radio-luminescent sources.Illumination sources may also include luminescent polymers. Anillumination source can produce electromagnetic radiation within thevisible spectrum, outside the visible spectrum, or a combination ofboth. A component illumination source is any illumination source that ispart of a lighting fixture.

“Lighting fixture” or “fixture” is any device or housing containing atleast one illumination source for the purposes of providingillumination.

“Color,” “temperature” and “spectrum” are used interchangeably withinthis document unless otherwise indicated. The three terms generallyrefer to the resultant combination of wavelengths of light that resultin the light produced by a lighting fixture. That combination ofwavelengths defines a color or temperature of the light. Color isgenerally used for light which is not white, while temperature is forlight that is white, but either term could be used for any type oflight. A white light has a color and a non-white light could have atemperature. A spectrum will generally refer to the spectral compositionof a combination of the individual wavelengths, while a color ortemperature will generally refer to the human perceived properties ofthat light. However, the above usages are not intended to limit thescope of these terms.

The recent advent of colored LEDs bright enough to provide illuminationhas prompted a revolution in illumination technology because of the easewith which the color and brightness of these light sources may bemodulated. One such modulation method is discussed in U.S. Pat. No.6,016,038 the entire disclosure of which is herein incorporated byreference. The systems and methods described herein discuss how to useand build LED light fixtures or systems, or other light fixtures orsystems utilizing component illumination sources. These systems havecertain advantages over other lighting fixtures. In particular, thesystems disclosed herein enable previously unknown control in the lightwhich can be produced by a lighting fixture. In particular, thefollowing disclosure discusses systems and methods for thepredetermination of the range of light, and type of light, that can beproduced by a lighting fixture and the systems and methods for utilizingthe predetermined range of that lighting fixture in a variety ofapplications.

To understand these systems and methods it is first useful to understanda lighting fixture which could be built and used in embodiments of thisinvention. FIG. 2 depicts one embodiment of a lighting module whichcould be used in one embodiment of the invention, wherein a lightingfixture (300) is depicted in block diagram format. The lighting fixture(300) includes two components, a processor (316) and a collection ofcomponent illumination sources (320), which is depicted in FIG. 2 as anarray of light emitting diodes. In one embodiment of the invention, thecollection of component illumination sources comprises at least twoillumination sources that produce different spectrums of light.

The collection of component illumination sources (320) are arrangedwithin said lighting fixture (300) on a mounting (310) in such a waythat the light from the different component illumination sources isallowed to mix to produce a resultant spectrum of light which isbasically the additive spectrum of the different component illuminationsources. In FIG. 2, this is done my placing the component illuminationsources (320) in a generally circular area; it could also be done in anyother manner as would be understood by one of skill in the art, such asa line of component illumination sources, or another geometric shape ofcomponent illumination sources.

The term “processor” is used herein to refer to any method or system forprocessing, for example, those that process in response to a signal ordata and/or those that process autonomously. A processor should beunderstood to encompass microprocessors, microcontrollers, programmabledigital signal processors, integrated circuits, computer-software,computer hardware, electrical circuits, application specific integratedcircuits, programmable logic devices, programmable gate arrays,programmable array logic, personal computers, chips, and any othercombination of discrete analog, digital, or programmable components, orother devices capable of providing processing functions.

The collection of illumination sources (320) is controlled by theprocessor (316) to produce controlled illumination. In particular, theprocessor (316) controls the intensity of different color individualLEDs in the array of LEDs so as to control the collection ofillumination sources (320) to produce illumination in any color within arange bounded by the spectra of the individual LEDs and any filters orother spectrum-altering devices associated therewith. Instantaneouschanges in color, strobing and other effects, can also be produced withlighting fixtures such as the light module (300) depicted in FIG. 2. Thelighting fixture (300) may be configured to receive power and data froman external source in one embodiment of the invention, the receipt ofsuch data being over data line (330) and power over power line (340).The lighting fixture (300), through the processor (316), may be made toprovide the various functions ascribed to the various embodiments of theinvention disclosed herein. In another embodiment, the processor (316)may be replaced by hard wiring or another type of control whereby thelighting fixture (300) produces only a single color of light.

Referring to FIG. 3, the lighting fixture (300) may be constructed to beused either alone or as part of a set of such lighting fixtures (300).An individual lighting fixture (300) or a set of lighting fixtures (300)can be provided with a data connection (350) to one or more externaldevices, or, in certain embodiments of the invention, with other lightmodules (300).

As used herein, the term “data connection” should be understood toencompass any system for delivering data, such as a network, a data bus,a wire, a transmitter and receiver, a circuit, a video tape, a compactdisc, a DVD disc, a video tape, an audio tape, a computer tape, a card,or the like. A data connection may thus include any system or method todeliver data by radio frequency, ultrasonic, auditory, infrared,optical, microwave, laser, electromagnetic, or other transmission orconnection method or system. That is, any use of the electromagneticspectrum or other energy transmission mechanism could provide a dataconnection as disclosed herein.

In an embodiment of the invention, the lighting fixture (300) may beequipped with a transmitter, receiver, or both to facilitatecommunication, and the processor (316) may be programmed to control thecommunication capabilities in a conventional manner. The light fixtures(300) may receive data over the data connection (350) from a transmitter(352), which may be a conventional transmitter of a communicationssignal, or may be part of a circuit or network connected to the lightingfixture (300). That is, the transmitter (352) should be understood toencompass any device or method for transmitting data to the lightfixture (300). The transmitter (352) may be linked to or be part of acontrol device (354) that generates control data for controlling thelight modules (300). In one embodiment of the invention, the controldevice (354) is a computer, such as a laptop computer.

The control data may be in any form suitable for controlling theprocessor (316) to control the collection of component illuminationsources (320). In one embodiment of the invention, the control data isformatted according to the DMX-512 protocol, and conventional softwarefor generating DMX-512 instructions is used on a laptop or personalcomputer as the control device (354) to control the lighting fixtures(300). The lighting fixture (300) may also be provided with memory forstoring instructions to control the processor (316), so that thelighting fixture (300) may act in stand alone mode according topre-programmed instructions.

The foregoing embodiments of a lighting fixture (300) will generallyreside in one of any number of different housings. Such housing is,however, not necessary, and the lighting fixture (300) could be usedwithout a housing to still form a lighting fixture. A housing mayprovide for lensing of the resultant light produced and may provideprotection of the lighting fixture (300) and its components. A housingmay be included in a lighting fixture as this term is used throughoutthis document.

FIG. 4 shows an exploded view of one embodiment of a lighting fixture ofthe present invention. The depicted embodiment comprises a substantiallycylindrical body section (362), a lighting fixture (364), a conductivesleeve (368), a power module (372), a second conductive sleeve (374),and an enclosure plate (378). It is to be assumed here that the lightingfixture (364) and the power module (372) contain the electricalstructure and software of lighting fixture (300), a different powermodule and lighting fixture (300) as known to the art, or as describedin U.S. patent application Ser. No. 09/215,624, the entire disclosure ofwhich is herein incorporated by reference. Screws (382), (384), (386),(388) allow the entire apparatus to be mechanically connected. Bodysection (362), conductive sleeves (368) and (374) and enclosure plate(378) are preferably made from a material that conducts heat, such asaluminum.

Body section (362) has an emission end (361), a reflective interiorportion (not shown) and an illumination end (363). Lighting module (364)is mechanically affixed to said illumination end (363). Said emissionend (361) may be open, or, in one embodiment may have affixed thereto afilter (391). Filter (391) may be a clear filter, a diffusing filter, acolored filter, or any other type of filter known to the art. In oneembodiment, the filter will be permanently attached to the body section(362), but in other embodiments, the filter could be removably attached.In a still further embodiment, the filter (391) need not be attached tothe emission end (361) of body portion (362) but may be insertedanywhere in the direction of light emission from the lighting fixture(364).

Lighting fixture (364) may be disk-shaped with two sides. Theillumination side (not shown) comprises a plurality of component lightsources which produce a predetermined selection of different spectrumsof light. The connection side may hold an electrical connector male pinassembly (392). Both the illumination side and the connection side canbe coated with aluminum surfaces to better allow the conduction of heatoutward from the plurality of component light sources to the bodysection (362). Likewise, power module (372) is generally disk shaped andmay have every available surface covered with aluminum for the samereason. Power module (372) has a connection side holding an electricalconnector female pin assembly (394) adapted to fit the pins fromassembly (392). Power module (172) has a power terminal side holding aterminal (398) for connection to a source of power such as an AC or DCelectrical source. Any standard AC or DC jack may be used, asappropriate.

Interposed between lighting fixture (364) and power module (372) is aconductive aluminum sleeve (368), which substantially encloses the spacebetween modules (362) and (372). As shown, a disk-shaped enclosure plate(378) and screws (382), (384), (386) and (388) can seal all of thecomponents together, and conductive sleeve (374) is thus interposedbetween enclosure plate (378) and power module (372). Alternatively, amethod of connection other than screws (382), (384), (386), and (388)may be used to seal the structure together. Once sealed together as aunit, the lighting fixture (362) may be connected to a data network asdescribed above and may be mounted in any convenient manner toilluminate an area.

FIGS. 5 a and 5 b show an alternative lighting fixture (5000) includinga housing that could be used in another embodiment of the invention. Thedepicted embodiment comprises a lower body section (5001), an upper bodysection (5003) and a lighting platform (5005). Again, the lightingfixture can contain the lighting fixture (300), a different lightingfixture known to the art, or a lighting fixture described anywhere elsein this document. The lighting platform (5005) shown here is designed tohave a linear track of component illumination devices (in this case LEDs(5007)) although such a design is not necessary. Such a design isdesirable for an embodiment of the invention, however. In addition,although the linear track of component illumination sources in depictedin FIG. 5 a as a single track, multiple linear tracks could be used aswould be understood by one of skill in the art. In one embodiment of theinvention, the upper body section (5003) can comprise a filter asdiscussed above, or may be translucent, transparent, semi-translucent,or semi-transparent.

Further shown in FIG. 5 a is the optional holder (5010) which may beused to hold the lighting fixture (5000). This holder (5010) comprisesclip attachments (5012) which may be used to frictionally engage thelighting fixture (5000) to enable a particular alignment of lightingfixture (5000) relative to the holder (5010). The mounting also containsattachment plate (5014) which may be attached to the clip attachments(5012) by any type of attachment known to the art whether permanent,removable, or temporary. Attachment plate (5014) may then be used toattach the entire apparatus to a surface such as, but not limited to, awall or ceiling.

In one embodiment, the lighting fixture (5000) is generally cylindricalin shape when assembled (as shown in FIG. 5 b) and therefore can move or“roll” on a surface. In addition, in one embodiment, the lightingfixture (5000) only can emit light through the upper body section (5003)and not through the lower body section (5001). Without a holder (5010),directing the light emitted from such a lighting fixture (5000) could bedifficult and motion could cause the directionality of the light toundesirably alter.

In one embodiment of the invention, it is recognized that prespecifiedranges of available colors may be desirable and it may also be desirableto build lighting fixtures in such a way as to maximize the illuminationof the lighting apparatus for particular color therein. This is bestshown through a numerical example. Let us assume that a lighting fixturecontains 30 component illumination sources in three differentwavelengths, primary red, primary blue, and primary green (such asindividual LEDs). In addition, let us assume that each of theseillumination sources produces the same intensity of light, they justproduce at different colors. Now, there are multiple different ways thatthe thirty illumination sources for any given lighting fixture can bechosen. There could be 10 of each of the illumination sources, oralternatively there could be 30 primary blue colored illuminationsources. It should be readily apparent that these light fixtures wouldbe useful for different types of lighting. The second light apparatusproduces more intense primary blue light (there are 30 sources of bluelight) than the first light source (which only has 10 primary blue lightsources, the remaining 20 light sources have to be off to produceprimary blue light), but is limited to only producing primary bluelight. The second light fixture can produce more colors of light,because the spectrums of the component illumination sources can be mixedin different percentages, but cannot produce as intense blue light. Itshould be readily apparent from this example that the selection of theindividual component illumination sources can change the resultantspectrum of light the fixture can produce. It should also be apparentthat the same selection of components can produce lights which canproduce the same colors, but can produce those colors at differentintensities. To put this another way, the full-on point of a lightingfixture (the point where all the component illumination sources are atmaximum) will be different depending on what the component illuminationsources are.

A lighting system may accordingly be specified using a full-on point anda range of selectable colors. This system has many potentialapplications such as, but not limited to, retail display lighting andtheater lighting. Often times numerous lighting fixtures of a pluralityof different colors are used to present a stage or other area withinteresting shadows and desirable features. Problems can arise, however,because lamps used regularly have similar intensities before lightingfilters are used to specify colors of those fixtures. Due to differencesin transmission of the various filters (for instance blue filters oftenloose significantly more intensity than red filters), lighting fixturesmust have their intensity controlled to compensate. For this reason,lighting fixtures are often operated at less than their full capability(to allow mixing) requiring additional lighting fixtures to be used.With the lighting fixtures of the instant invention, the lightingfixtures can be designed to produce particular colors at identicalintensities of chosen colors when operating at their full potential;this can allow easier mixing of the resultant light, and can result inmore options for a lighting design scheme.

Such a system enables the person building or designing lighting fixturesto generate lights that can produce a pre-selected range of colors,while still maximizing the intensity of light at certain more desirablecolors. These lighting fixtures would therefore allow a user to selectcertain color(s) of lighting fixtures for an application independent ofrelative intensity. The lighting fixtures can then be built so that theintensities at these colors are the same. Only the spectrum is altered.It also enables a user to select lighting fixtures that produce aparticular high-intensity color of light, and also have the ability toselect nearby colors of light in a range.

The range of colors which can be produced by the lighting fixture can bespecified instead of, or in addition to, the full-on point. The lightingfixture can then be provided with control systems that enable a user ofthe lighting fixture to intuitively and easily select a desired colorfrom the available range.

One embodiment of such a system works by storing the spectrums of eachof the component illumination sources. In this example embodiment, theillumination sources are LEDs. By selecting different component LEDswith different spectrums, the designer can define the color range of alighting fixture. An easy way to visualize the color range is to use theCIE diagram which shows the entire lighting range of all colors of lightwhich can exist. One embodiment of a system provides a light-authoringinterface such as an interactive computer interface.

FIG. 6 shows an embodiment of an interactive computer interface enablinga user to see a CIE diagram (508) on which is displayed the spectrum ofcolor a lighting fixture can produce. In FIG. 6 individual LED spectraare saved in memory and can be recalled from memory to be used forcalculating a combined color control area. The interface has severalchannels (502) for selecting LEDs. Once selected, varying the intensityslide bar (504) can change the relative number of LEDs of that type inthe resultant lighting fixture. The color of each LED is represented ona color chart such as a CIE diagram (508) as a point (for example, point(506)). A second LED can be selected on a different channel to create asecond point (for example, point (501)) on the CIE chart. A lineconnecting these two points represents the extent that the color fromthese two LEDs can be mixed to produce additional colors. When a thirdand fourth channel are used, an area (510) can be plotted on the CIEdiagram representing the possible combinations of the selected LEDs.Although the area (510) shown here is a polygon of four sides it wouldbe understood by one of skill in the art that the area (510) could be apoint line or a polygon with any number of sides depending on the LEDschosen.

In addition to specifying the color range, the intensities at any givencolor can be calculated from the LED spectrums. By knowing the number ofLEDs for a given color and the maximum intensity of any of these LEDs,the total light output at a particular color is calculated. A diamond orother symbol (512) may be plotted on the diagram to represent the colorwhen all of the LEDs are on full brightness or the point may representthe present intensity setting.

Because a lighting fixture can be made of a plurality of componentillumination sources, when designing a lighting fixture, a color that ismost desirable can be selected, and a lighting fixture can be designedthat maximizes the intensity of that color. Alternatively, a fixture maybe chosen and the point of maximum intensity can be determined from thisselection. A tool may be provided to allow calculation of a particularcolor at a maximum intensity. FIG. 6 shows such a tool as symbol (512),where the CIE diagram has been placed on a computer and calculations canbe automatically performed to compute a total number of LEDs necessaryto produce a particular intensity, as well as the ratio of LEDs ofdifferent spectrums to produce particular colors. Alternatively, aselection of LEDs may be chosen and the point of maximum intensitydetermined; both directions of calculation are included in embodimentsof this invention.

In FIG. 6 as the number of LEDs are altered, the maximum intensitypoints move so that a user can design a light which has a maximumintensity at a desired point.

Therefore the system in one embodiment of the invention contains acollection of the spectrums of a number of different LEDs, provides aninterface for a user to select LEDs that will produce a range of colorthat encloses the desirable area, and allows a user to select the numberof each LED type such that when the unit is on full, a target color isproduced. In an alternative embodiment, the user would simply need toprovide a desired spectrum, or color and intensity, and the system couldproduce a lighting fixture which could generate light according to therequests.

Once the light has been designed, in one embodiment, it is furtherdesirable to make the light's spectrum easily accessible to the lightingfixture's user. As was discussed above, the lighting fixture may havebeen chosen to have a particular array of illumination sources such thata particular color is obtained at maximum intensity. However, there maybe other colors that can be produced by varying the relative intensitiesof the component illumination sources. The spectrum of the lightingfixture can be controlled within the predetermined range specified bythe area (510). To control the lighting color within the range, it isrecognized that each color within the polygon is the additive mix of thecomponent LEDs with each color contained in the components having avaried intensity. That is, to move from one point in FIG. 6 to a secondpoint in FIG. 6, it is necessary to alter the relative intensities ofthe component LEDs. This may be less than intuitive for the final userof the lighting fixture who simply wants a particular color, or aparticular transition between colors and does not know the relativeintensities to shift to. This is particularly true if the LEDs used donot have spectra with a single well-determined peak of color. A lightingfixture may be able to generate several shades of orange, but how to getto each of those shades may require control.

In order to be able to carry out such control of the spectrum of thelight, it is desirable in one embodiment to create a system and methodfor linking the color of the light to a control device for controllingthe light's color. Since a lighting fixture can be custom designed, itmay, in one embodiment, be desirable to have the intensities of each ofthe component illumination sources “mapped” to a desirable resultantspectrum of light and allowing a point on the map to be selected by thecontroller. That is, a method whereby, with the specification of aparticular color of light by a controller, the lighting fixture can turnon the appropriate illumination sources at the appropriate intensity tocreate that color of light. In one embodiment, the lighting fixturedesign software shown in FIG. 6 can be configured in such a way that itcan generate a mapping between a desirable color that can be produced(within the area (510)), and the intensities of the component LEDs thatmake up the lighting fixture. This mapping will generally take one oftwo forms: 1) a lookup table, or 2) a parametric equation, althoughother forms could be used as would be known to one of skill in the art.Software on board the lighting fixture (such as in the processor (316)above) or on board a lighting controller, such as one of those known tothe art, or described above, can be configured to accept the input of auser in selecting a color, and producing a desired light.

This mapping may be performed by a variety of methods. In oneembodiment, statistics are known about each individual componentillumination sources within the lighting fixture, so mathematicalcalculations may be made to produce a relationship between the resultingspectrum and the component spectrums. Such calculations would be wellunderstood by one of skill in the art.

In another embodiment, an external calibration system may be used. Onelayout of such a system is disclosed in FIG. 7. Here the calibrationsystem includes a lighting fixture (2010) that is connected to aprocessor (2020) and which receives input from a light sensor ortransducer (2034). The processor (2020) may be processor (316) or may bean additional or alternative processor. The sensor (2034) measures colorcharacteristics, and optionally brightness, of the light output by thelighting fixture (2010) and/or the ambient light, and the processor(2020) varies the output of the lighting fixture (2010). Between thesetwo devices modulating the brightness or color of the output andmeasuring the brightness and color of the output, the lighting fixturecan be calibrated where the relative settings of the componentillumination sources (or processor settings (2020)) are directly relatedto the output of the fixture (2010) (the light sensor (2034) settings).Since the sensor (2034) can detect the net spectrum produced by thelighting fixture, it can be used to provide a direct mapping by relatingthe output of the lighting fixture to the settings of the componentLEDs.

Once the mapping has been completed, other methods or systems may beused for the light fixture's control. Such methods or systems willenable the determination of a desired color, and the production by thelighting fixture of that color.

FIG. 8 a shows one embodiment of the system (2000) where a controlsystem (2030) may be used in conjunction with a lighting fixture (2010)to enable control of the lighting fixture (2010). The control system(2030) may be automatic, may accept input from a user, or may be anycombination of these two. The system (2000) may also include a processor(2020) which may be processor (316) or another processor to enable thelight to change color.

FIG. 9 shows a more particular embodiment of a system (2000). A usercomputer interface control system (2032) with which a user may select adesired color of light is used as a control system (2030). The interfacecould enable any type of user interaction in the determination of color.For example, the interface may provide a palette, chromaticity diagram,or other color scheme from which a user may select a color, e.g., byclicking with a mouse on a suitable color or color temperature on theinterface, changing a variable using a keyboard, etc. The interface mayinclude a display screen, a computer keyboard, a mouse, a trackpad, orany other suitable system for interaction between the processor and auser. In certain embodiments, the system may permit a user to select aset of colors for repeated use, capable of being rapidly accessed, e.g.,by providing a simple code, such as a single letter or digit, or byselecting one of a set of preset colors through an interface asdescribed above. In certain embodiments, the interface may also includea look-up table capable of correlating color names with approximateshades, converting color coordinates from one system, (e.g., RGB, CYM,YIQ, YUV, HSV, HLS, XYZ, etc.) to a different color coordinate system orto a display or illumination color, or any other conversion function forassisting a user in manipulating the illumination color. The interfacemay also include one or more closed-form equations for converting from,for example, a user-specified color temperature (associated with aparticular color of white light) into suitable signals for the differentcomponent illumination sources of the lighting fixture (2010). Thesystem may further include a sensor as discussed below for providinginformation to the processor (2020), e.g., for automatically calibratingthe color of emitted light of the lighting fixture (2010) to achieve thecolor selected by the user on the interface.

In another embodiment, a manual control system (2031) is used in thesystem (2000), as depicted in FIG. 10 a, such as a dial, slider, switch,multiple switch, console, other lighting control unit, or any othercontroller or combination of controllers to permit a user to modify theillumination conditions until the illumination conditions or theappearance of a subject being illuminated is desirable. For example, adial or slider may be used in a system to modulate the net colorspectrum produced, the illumination along the color temperature curve,or any other modulation of the color of the lighting fixture.Alternatively, a joystick, trackball, trackpad, mouse, thumb-wheel,touch-sensitive surface, or a console with two or more sliders, dials,or other controls may be used to modulate the color, temperature, orspectrum. These manual controls may be used in conjunction with acomputer interface control system (2032) as discussed above, or may beused independently, possibly with related markings to enable a user toscan through an available color range.

One such manual control system (2036) is shown in greater detail in FIG.10 b. The depicted control unit features a dial marked to indicate arange of color temperatures, e.g., from 3000K to 10,500K. This devicewould be useful on a lighting fixture used to produce a range oftemperatures (“colors”) of white light. It would be understood by one ofskill in the art that broader, narrower, or overlapping ranges may beemployed, and a similar system could be employed to control lightingfixtures that can produce light of a spectrum beyond white, or notincluding white. A manual control system (2036) may be included as partof a processor controlling an array of lighting units, coupled to aprocessor, e.g., as a peripheral component of a lighting control system,disposed on a remote control capable of transmitting a signal, such asan infrared or microwave signal, to a system controlling a lightingunit, or employed or configured in any other manner, as will readily beunderstood by one of skill in the art.

Additionally, instead of a dial, a manual control system (2036) mayemploy a slider, a mouse, or any other control or input device suitablefor use in the systems and methods described herein.

In another embodiment, the calibration system depicted in FIG. 7 mayfunction as a control system or as a portion of a control system. Forinstance a selected color could be input by the user and the calibrationsystem could measure the spectrum of ambient light; compare the measuredspectrum with the selected spectrum, adjust the color of light producedby the lighting fixture (2010), and repeat the procedure to minimize thedifference between the desired spectrum and the measured spectrum. Forexample, if the measured spectrum is deficient in red wavelengths whencompared with the target spectrum, the processor may increase thebrightness of red LEDs in the lighting fixture, decrease the brightnessof blue and green LEDs in the lighting fixture, or both, in order tominimize the difference between the measured spectrum and the targetspectrum and potentially also achieve a target brightness (i.e. such asthe maximum possible brightness of that color). The system could also beused to match a color produced by a lighting fixture to a color existingnaturally. For instance, a film director could find light in a locationwhere filming does not occur and measure that light using the sensor.This could then provide the desired color which is to be produced by thelighting fixture. In one embodiment, these tasks can be performedsimultaneously (potentially using two separate sensors). In a yetfurther embodiment, the director can remotely measure a lightingcondition with a sensor (2034) and store that lighting condition onmemory associated with that sensor (2034). The sensor's memory may thenbe transferred at a later time to the processor (2020) which may set thelighting fixture to mimic the light recorded. This allows a director tocreate a “memory of desired lighting” which can be stored and recreatedlater by lighting fixtures such as those described above.

The sensor (2034) used to measure the illumination conditions may be aphotodiode, a phototransistor, a photoresistor, a radiometer, aphotometer, a calorimeter, a spectral radiometer, a camera, acombination of two or more of the preceding devices, or any other systemcapable of measuring the color or brightness of illumination conditions.An example of a sensor may be the IL2000 SpectroCube Spectroradiometeroffered for sale by International Light Inc., although any other sensormay be used. A colorimeter or spectral radiometer is advantageousbecause a number of wavelengths can be simultaneously detected,permitting accurate measurements of color and brightness simultaneously.A color temperature sensor which may be employed in the systems methodsdescribed herein is disclosed in U.S. Pat. No. 5,521,708.

In embodiments wherein the sensor (2034) detects an image, e.g.,includes a camera or other video capture device, the processor (2020)may modulate the illumination conditions with the lighting fixture(2010) until an illuminated object appears substantially the same, e.g.,of substantially the same color, as in a previously recorded image. Sucha system simplifies procedures employed by cinematographers, forexample, attempting to produce a consistent appearance of an object topromote continuity between scenes of a film, or by photographers, forexample, trying to reproduce lighting conditions from an earlier shoot.

In certain embodiments, the lighting fixture (2010) may be used as thesole light source, while in other embodiments, such as is depicted inFIG. 8 b, the lighting fixture (2010) may be used in combination with asecond source of light (2040), such as an incandescent, fluorescent,halogen, or other LED sources or component light sources (includingthose with and without control), lights that are controlled with pulsewidth modulation, sunlight, moonlight, candlelight, etc. This use can beto supplement the output of the second source. For example, afluorescent light emitting illumination weak in red portions of thespectrum may be supplemented with a lighting fixture emitting primarilyred wavelengths to provide illumination conditions more closelyresembling natural sunlight. Similarly, such a system may also be usefulin outdoor image capture situations, because the color temperature ofnatural light varies as the position of the sun changes. A lightingfixture (2010) may be used in conjunction with a sensor (2034) ascontroller (2030) to compensate for changes in sunlight to maintainconstant illumination conditions for the duration of a session.

Any of the above systems could be deployed in the system disclosed inFIG. 11. A lighting system for a location may comprise a plurality oflighting fixtures (2301) which are controllable by a central controlsystem (2303). The light within the location (or on a particularlocation such as the stage (2305) depicted here) is now desired to mimicanother type of light such as sunlight. A first sensor (2307) is takenoutside and the natural sunlight (2309) is measured and recorded. Thisrecording is then provided to central control system (2303). A secondsensor (which may be the same sensor in one embodiment) (2317) ispresent on the stage (2305). The central control system (2303) nowcontrols the intensity and color of the plurality of lighting fixtures(2301) and attempts to match the input spectrum of said second sensor(2317) with the prerecorded natural sunlight's (2309) spectrum. In thismanner, interior lighting design can be dramatically simplified asdesired colors of light can be reproduced or simulated in a closedsetting. This can be in a theatre (as depicted here), or in any otherlocation such as a home, an office, a soundstage, a retail store, or anyother location where artificial lighting is used. Such a system couldalso be used in conjunction with other secondary light sources to createa desired lighting effect.

The above systems allow for the creation of lighting fixtures withvirtually any type of spectrum. It is often desirable to produce lightthat appears “natural” or light which is a high-quality, especiallywhite light.

A lighting fixture which produces white light according to the aboveinvention can comprise any collection of component illumination sourcessuch that the area defined by the illumination sources can encapsulateat least a portion of the black body curve. The black body curve (104)in FIG. 1 is a physical construct that shows different color white lightwith regards to the temperature of the white light. In a preferredembodiment, the entire black body curve would be encapsulated allowingthe lighting fixture to produce any temperature of white light.

For a variable color white light with the highest possible intensity, asignificant portion of the black body curve may be enclosed. Theintensity at different color whites along the black body curve can thenbe simulated. The maximum intensity produced by this light could beplaced along the black body curve. By varying the number of each colorLED (in FIG. 6 red, blue, amber, and blue-green) it is possible tochange the location of the full-on point (the symbol (512) in FIG. 6).For example, the full-on color could be placed at approximately 5400K(noon day sunlight shown by point (106) in FIG. 1), but any other pointcould be used (two other points are shown in FIG. 1 corresponding to afire glow and an incandescent bulb). Such a lighting apparatus wouldthen be able to produce 5400 K light at a high intensity; in addition,the light may adjust for differences in temperature (for instance cloudysunlight) by moving around in the defined area.

Although this system generates white light with a variable colortemperature, it is not necessarily a high quality white light source. Anumber of combinations of colors of illumination sources can be chosenwhich enclose the black body curve, and the quality of the resultinglighting fixtures may vary depending on the illumination sources chosen.

Since white light is a mixture of different wavelengths of light, it ispossible to characterize white light based on the component colors oflight that are used to generate it. Red, green, and blue (RGB) cancombine to form white; as can light blue, amber, and lavender; or cyan,magenta and yellow. Natural white light (sunlight) contains a virtuallycontinuous spectrum of wavelengths across the human visible band (andbeyond). This can be seen by examining sunlight through a prism, orlooking at a rainbow. Many artificial white lights are technically whiteto the human eye, however, they can appear quite different when shown oncolored surfaces because they lack a virtually continuous spectrum.

As an extreme example one could create a white light source using twolasers (or other narrow band optical sources) with complimentarywavelengths. These sources would have an extremely narrow spectral widthperhaps 1 nm wide. To exemplify this, we will choose wavelengths of 635nm and 493 nm. These are considered complimentary since they willadditively combine to make light which the human eye perceives as whitelight. The intensity levels of these two lasers can be adjusted to someratio of powers that will produce white light that appears to have acolor temperature of 5000K. If this source were directed at a whitesurface, the reflected light will appear as 5000K white light.

The problem with this type of white light is that it will appearextremely artificial when shown on a colored surface. A colored surface(as opposed to colored light) is produced because the surface absorbsand reflects different wavelengths of light. If hit by white lightcomprising a full spectrum (light with all wavelengths of the visibleband at reasonable intensity), the surface will absorb and reflectperfectly. However, the white light above does not provide the completespectrum. To again use an extreme example, if a surface only reflectedlight from 500 nm-550 nm it will appear a fairly deep green infull-spectrum light, but will appear black (it absorbs all the spectrumspresent) in the above described laser-generated artificial white light.

Further, since the CRI index relies on a limited number of observations,there are mathematical loopholes in the method. Since the spectrums forCRI color samples are known, it is a relatively straightforward exerciseto determine the optimal wavelengths and minimum numbers of narrow bandsources needed to achieve a high CRI. This source will fool the CRImeasurement, but not the human observer. The CRI method is at best anestimator of the spectrum that the human eye can see. An everydayexample is the modern compact fluorescent lamp. It has a fairly high CRIof 80 and a color temperature of 2980K but still appears unnatural. Thespectrum of a compact fluorescent is shown in FIG. 27.

Due to the desirability of high-quality light (in particularhigh-quality white light) that can be varied over different temperaturesor spectrums, a further embodiment of this invention comprises systemsand method for generating higher-quality white light by mixing theelectromagnetic radiation from a plurality of component illuminationsources such as LEDs. This is accomplished by choosing LEDs that providea white light that is targeted to the human eye's interpretation oflight, as well as the mathematical CRI index. That light can then bemaximized in intensity using the above system. Further, because thecolor temperature of the light can be controlled, this high qualitywhite light can therefore still have the control discussed above and canbe a controllable, high-quality, light which can produce high-qualitylight across a range of colors.

To produce a high-quality white light, it is necessary to examine thehuman eye's ability to see light of different wavelengths and determinewhat makes a light high-quality. In it's simplest definition, ahigh-quality white light provides low distortion to colored objects whenthey are viewed under it. It therefore makes sense to begin by examininga high-quality light based on what the human eye sees. Generally thehighest quality white light is considered to be sunlight orfull-spectrum light, as this is the only source of “natural” light. Forthe purposes of this disclosure, it will be accepted that sunlight is ahigh-quality white light.

The sensitivity of the human eye is known as the Photopic response. ThePhotopic response can be thought of as a spectral transfer function forthe eye, meaning that it indicates how much of each wavelength of lightinput is seen by the human observer. This sensitivity can be expressedgraphically as the spectral luminosity function Vλ (501), which isrepresented in FIG. 12.

The eye's Photopic response is important since it can be used todescribe the boundaries on the problem of generating white light (or ofany color of light). In one embodiment of the invention, a high qualitywhite light will need to comprise only what the human eye can “see.” Inanother embodiment of the invention, it can be recognized thathigh-quality white light may contain electromagnetic radiation whichcannot be seen by the human eye but may result in a photobiologicalresponse. Therefore a high-quality white light may include only visiblelight, or may include visible light and other electromagnetic radiationwhich may result in a photobiological response. This will generally beelectromagnetic radiation less than 400 nm (ultraviolet light) orgreater than 700 nm (infrared light).

Using the first part of the description, the source is not required tohave any power above 700 nm or below 400 nm since the eye has onlyminimal response at these wavelengths. A high-quality source wouldpreferably be substantially continuous between these wavelengths(otherwise colors could be distorted) but can fall-off towards higher orlower wavelengths due to the sensitivity of the eye. Further, thespectral distribution of different temperatures of white light will bedifferent. To illustrate this, spectral distributions for two blackbodysources with temperatures of 5000K (601) and 2500K (603) are shown inFIG. 13 along with the spectral luminosity function (501) from FIG. 12.

As seen in FIG. 13, the 5000K curve is smooth and centered about 555 nmwith only a slight fall-off in both the increasing and decreasingwavelength directions. The 2500K curve is heavily weighted towardshigher wavelengths. This distribution makes sense intuitively, sincelower color temperatures appear to be yellow-to-reddish. One point thatarises from the observation of these curves, against the spectralluminosity curve, is that the Photopic response of the eye is “filled.”This means that every color that is illuminated by one of these sourceswill be perceived by a human observer. Any holes, i.e., areas with nospectral power, will make certain objects appear abnormal. This is whymany “white” light sources seem to disrupt colors. Since the blackbodycurves are continuous, even the dramatic change from 5000K to 2500K willonly shift colors towards red, making them appear warmer but not devoidof color. This comparison shows that an important specification of anyhigh-quality artificial light fixture is a continuous spectrum acrossthe photopic response of the human observer.

Having examined these relationships of the human eye, a fixture forproducing controllable high-quality white light would need to have thefollowing characteristic. The light has a substantially continuousspectrum over the wavelengths visible to the human eye, with any holesor gaps locked in the areas where the human eye is less responsive. Inaddition, in order to make a high-quality white light controllable overa range of temperatures, it would be desirable to produce a lightspectrum which can have relatively equal values of each wavelength oflight, but can also make different wavelengths dramatically more or lessintense with regards to other wavelengths depending on the colortemperature desired. The clearest waveform which would have such controlwould need to mirror the scope of the photopic response of the eye,while still being controllable at the various different wavelengths.

As was discussed above, the traditional mixing methods which createwhite light can create light which is technically “white” but sillproduces an abnormal appearance to the human eye. The CRI rating forthese values is usually extremely low or possibly negative. This isbecause if there is not a wavelength of light present in the generationof white light, it is impossible for an object of a color toreflect/absorb that wavelength. In an additional case, since the CRIrating relies on eight particular color samples, it is possible to get ahigh CRI, while not having a particularly high-quality light because thewhite light functions well for those particular color samples specifiedby the CRI rating. That is, a high CRI index could be obtained by awhite light composed of eight 1 nm sources which were perfectly lined upwith the eight CRI color structures. This would, however, not be ahigh-quality light source for illuminating other colors.

The fluorescent lamp shown in FIG. 27 provides a good example of a highCRI light that is not high-quality. Although the light from afluorescent lamp is white, it is comprised of many spikes (such as (201)and (203)). The position of these spikes has been carefully designed sothat when measured using the CRI samples they yield a high rating. Inother words, these spikes fool the CRI calculation but not the humanobserver. The result is a white light that is usable but not optimal(i.e., it appears artificial). The dramatic peaks in the spectrum of afluorescent light are also clear in FIG. 27. These peaks are part of thereason that fluorescent light looks very artificial. Even if light isproduced within the spectral valleys, it is so dominated by the peaksthat a human eye has difficulty seeing it. A high-quality white lightmay be produced according to this disclosure without the dramatic peaksand valleys of a florescent lamp.

A spectral peak is the point of intensity of a particular color of lightwhich has less intensity at points immediately to either side of it. Amaximum spectral peak is the highest spectral peak within the region ofinterest. It is therefore possible to have multiple peaks within achosen portion of the electromagnetic spectrum, only a single maximumpeak, or to have no peaks at all. For instance, FIG. 12 in the region500 nm to 510 nm has no spectral peaks because there is no point in thatregion that has lower points on both sides of it.

A valley is the opposite of a peak and is a point that is a minimum andhas points of higher intensity on either side of it (an inverted plateauis also a valley). A special plateau can also be a spectrum peak. Aplateau involves a series of concurrent points of the same intensitywith the points on either side of the series having less intensity.

It should be clear that high-quality white light simulating black-bodysources do not have significant peaks and valleys within the area of thehuman eye's photopic response as is shown in FIG. 13.

Most artificial light, does however have some peaks and valleys in thisregion such shown in FIG. 27, however the less difference between thesepoints the better. This is especially true for higher temperature lightwhereas for lower temperature light the continuous line has a positiveupward slope with no peaks or valleys and shallow valleys in the shorterwavelength areas would be less noticeable, as would slight peaks in thelonger wavelengths.

To take into account this peak and valley relationship to high-qualitywhite light, the following is desirable in a high-quality white light ofone embodiment of this invention. The lowest valley in the visible rangeshould have a greater intensity than the intensity attributable tobackground noise as would be understood by one of skill in the art. Itis further desirable to close the gap between the lowest valley and themaximum peak; and other embodiments of the invention have lowest valleyswith at least 5% 10%, 25%, 33%, 50% and 75% of the intensity of themaximum peaks. One skilled in the art would see that other percentagescould be used anywhere up to 100%.

In another embodiment, it is desirable to mimic the shape of the blackbody spectra at different temperatures; for higher temperatures (4,000 Kto 10,000 K) this may be similar to the peaks and valleys analysisabove. For lower temperatures, another analysis would be that mostvalleys should be at a shorter wavelength than the highest peak. Thiswould be desirable in one embodiment for color temperatures less than2500 K. In another embodiment it would be desirable to have this in theregion 500 K to 2500 K.

From the above analysis high-quality artificial white light shouldtherefore have a spectrum that is substantially continuous between the400 nm and 700 nm without dramatic spikes. Further, to be controllable,the light should be able to produce a spectrum that resembles naturallight at various color temperatures. Due to the use of mathematicalmodels in the industry, it is also desirable for the source to yield ahigh CRI indicative that the reference colors are being preserved andshowing that the high-quality white light of the instant invention doesnot fail on previously known tests.

In order to build a high-quality white light lighting fixture using LEDsas the component illumination sources, it is desirable in one embodimentto have LEDs with particular maximum spectral peaks and spectral widths.It is also desirable to have the lighting fixture allow forcontrollability, that is that the color temperature can be controlled toselect a particular spectrum of “white” light or even to have a spectrumof colored light in addition to the white light. It would also bedesirable for each of the LEDs to produce equal intensities of light toallow for easy mixing.

One system for creating white light includes a large number (for examplearound 300) of LEDs, each of which has a narrow spectral width and eachof which has a maximum spectral peak spanning a predetermined portion ofthe range from about 400 nm to about 700 nm, possibly with some overlap,and possibly beyond the boundaries of visible light. This light sourcemay produce essentially white light, and may be controllable to produceany color temperature (and also any color). It allows for smallervariation than the human eye can see and therefore the light fixture canmake changes more finely than a human can perceive. Such a light fixtureis therefore one embodiment of the invention but other embodiments canuse fewer LEDs when perception by humans is the focus.

In another embodiment of the invention, a significantly smaller numberof LEDs can be used with the spectral width of each LED increased togenerate a high-quality white light. One embodiment of such a lightfixture is shown in FIG. 14. FIG. 14 shows the spectrums of nine LEDs(701) with 25 nm spectral widths spaced every 25 nm. It should berecognized here that a nine LED lighting fixture does not necessarilycontain exactly nine total illumination sources. It contains some numberof each of nine different colored illuminating sources. This number willusually be the same for each color, but need not be. High-brightnessLEDs with a spectral width of about 25 nm are generally available. Thesolid line (703) indicates the additive spectrum of all of the LEDspectrums at equal power as could be created using the above methodlighting fixture. The powers of the LEDs may be adjusted to generate arange of color temperature (and colors as well) by adjusting therelative intensities of the nine LEDs. FIGS. 15 a and 15 b are spectrumsfor the 5000K (801) and 2500K (803) white-light from this lightingfixture. This nine LED lighting fixture has the ability to reproduce awide range of color temperatures as well as a wide range of colors asthe area of the CIE diagram enclosed by the component LEDs covers mostof the available colors. It enables control over the production ofnon-continuous spectrums and the generation of particular high-qualitycolors by choosing to use only a subset of the available LEDillumination sources. It should be noted that the choice of location ofthe dominant wavelength of the nine LEDs could be moved withoutsignificant variation in the ability to produce white light. Inaddition, different colored LEDs may be added. Such additions mayimprove the resolution as was discussed in the 300 LED example above.Any of these light fixtures may meet the quality standards above. Theymay produce a spectrum that is continuous over the photopic response ofthe eye, that is without dramatic peaks, and that can be controlled toproduce a white light of multiple desired color temperatures.

The nine LED white light source is effective since its spectralresolution is sufficient to accurately simulate spectral distributionswithin human-perceptible limits. However, fewer LEDs may be used. If thespecifications of making high-quality white light are followed, thefewer LEDs may have an increased spectral width to maintain thesubstantially continuous spectrum that fills the Photopic response ofthe eye. The decrease could be from any number of LEDs from 8 to 2. The1 LED case allows for no color mixing and therefore no control. To havea temperature controllable white light fixture at least two colors ofLEDs may be required.

One embodiment of the current invention includes three different coloredLEDs. Three LEDs allow for a two dimensional area (a triangle) to beavailable as the spectrum for the resultant fixture. One embodiment of athree LED source is shown in FIG. 16.

The additive spectrum of the three LEDs (903) offers less control thanthe nine LED lighting fixture, but may meet the criteria for ahigh-quality white light source as discussed above. The spectrum may becontinuous without dramatic peaks. It is also controllable, since thetriangle of available white light encloses the black body curve. Thissource may lose fine control over certain colors or temperatures thatwere obtained with a greater number of LEDs as the area enclosed on theCIE diagram is a triangle, but the power of these LEDs can still becontrolled to simulate sources of different color temperatures. Such analteration is shown in FIGS. 17 a and 17 b for 5000K (1001) and 2500K(1003) sources. One skilled in the art would see that alternativetemperatures may also be generated.

Both the nine LED and three LED examples demonstrate that combinationsof LEDs can be used to create high-quality white lighting fixtures.These spectrums fill the photopic response of the eye and arecontinuous, which means they appear more natural than artificial lightsources such as fluorescent lights. Both spectra may be characterized ashigh-quality since the CRIs measure in the high 90s.

In the design of a white lighting fixture, one impediment is the lack ofavailability for LEDs with a maximum spectral peak of 555 nm. Thiswavelength is at the center of the Photopic response of the eye and oneof the clearest colors to the eye. The introduction of an LED with adominant wavelength at or near 555 nm would simplify the generation ofLED-based white light, and a white light fixture with such an LEDcomprises one embodiment of this invention. In another embodiment of theinvention, a non-LED illumination source that produces light with amaximum spectral peak from about 510 nm to about 570 nm could also beused to fill this particular spectral gap. In a still furtherembodiment, this non-LED source could comprise an existing white lightsource and a filter to make that resulting light source have a maximumspectral peak in this general area.

In another embodiment high-quality white light may be generated usingLEDs without spectral peaks around 555 nm to fill in the gap in thePhotopic response left by the absence of green LEDs. One possibility isto fill the gap with a non-LED illumination source. Another, asdescribed below, is that a high-quality controllable white light sourcecan be generated using a collection of one or more different coloredLEDs where none of the LEDs have a maximum spectral peak in the range ofabout 510 nm to 570 nm.

To build a white light lighting fixture that is controllable over agenerally desired range of color temperatures, it is first necessary todetermine the criteria of temperature desired.

In one embodiment, this is chosen to be color temperatures from about2300K to about 4500K which is commonly used by lighting designers inindustry. However, any range could be chosen for other embodimentsincluding the range from 500K to 10,000K which covers most variation invisible white light or any sub-range thereof. The overall outputspectrum of this light may achieve a CRI comparable to standard lightsources already existing. Specifically, a high CRI (greater than 80) at4500K and lower CRI (greater than 50) at 2300K may be specified althoughagain any value could be chosen. Peaks and valleys may also be minimizedin the range as much as possible and particularly to have a continuouscurve where no intensity is zero (there is at least some spectralcontent at each wavelength throughout the range).

In recent years, white LEDs have become available. These LEDs operateusing a blue LED to pump a layer of phosphor. The phosphor down-covertssome of the blue light into green and red. The result is a spectrum thathas a wide spectrum and is roughly centered about 555 nm, and isreferred to as “cool white.” An example spectrum for such a white LED(in particular for a Nichia NSPW510 BS (bin A) LED), is shown in FIG. 18as the spectrum (1201).

The spectrum (1201) shown in FIG. 18 is different from the Gaussian-likespectrums for some LEDs. This is because not all of the pump energy fromthe blue LED is down-converted. This has the effect of cooling theoverall spectrum since the higher portion of the spectrum is consideredto be warm. The resulting CRI for this LED is 84 but it has a colortemperature of 20,000K. Therefore the LED on its own does not meet theabove lighting criteria. This spectrum (1201) contains a maximumspectral peak at about 450 nm and does not accurately fill the photopicresponse of the human eye. A single LED also allows for no control ofcolor temperature and therefore a system of the desired range of colortemperatures cannot be generated with this LED alone.

Nichia Chemical currently has three bins (A, B, and C) of white LEDsavailable. The LED spectrum (1201) shown in FIG. 18 is the coolest ofthese bins. The warmest LED is bin C (the spectrum (1301) of which ispresented in FIG. 19). The CRI of this LED is also 84; it has a maximumspectral peak of around 450 nm, and it has a CCT of 5750K. Using acombination of the bin A or C LEDs will enable the source to fill thespectrum around the center of the Photopic response, 555 nm. However,the lowest achievable color temperature will be 5750K (from using thebin C LED alone) which does not cover the entire range of colortemperatures previously discussed. This combination will appearabnormally cool (blue) on its own as the additive spectrum will stillhave a significant peak around 450 nm.

The color temperature of these LEDs can be shifted using an opticalhigh-pass filter placed over the LEDs. This is essentially a transparentpiece of glass or plastic tinted so as to enable only higher wavelengthlight to pass through. One example of such a high-pass filter'stransmission is shown in FIG. 20 as line (1401). Optical filters areknown to the art and the high pass filter will generally comprise atranslucent material, such as plastics, glass, or other transmissionmedia which has been tinted to form a high pass filter such as the oneshown in FIG. 20. One embodiment of the invention includes generating afilter of a desired material (to obtain particular physical properties)upon specifying the desired optical properties. This filter may beplaced over the LEDs directly, or may be filter (391) from the lightingfixture's housing.

One embodiment of the invention allows for the existing fixture to havea preselection of component LEDs and a selection of different filters.These filters may shift the range of resultant colors without alterationof the LEDs. In this way a filter system may be used in conjunction withthe selected LEDs to fill an area of the CIE enclosed (area (510)) by alight fixture that is shifted with respect to the LEDs, thus permittingan additional degree of control. In one embodiment, this series offilters could enable a single light fixture to produce white light ofany temperature by specifying a series of ranges for various filterswhich, when combined, enclose the white line. One embodiment of this isshown in FIG. 30 where a selection of areas (3001, 3011, 3021, 3031)depends on the choice of filters shifting the enclosed area.

This spectral transmission measurement shows that the high pass filterin FIG. 20 absorbs spectral power below 500 nm. It also shows an overallloss of approximately 10% which is expected. The dotted line (1403) inFIG. 20 shows the transmission loss associated with a standardpolycarbonate diffuser which is often used in light fixtures. It is tobe expected that the light passing through any substance will result insome decrease in intensity.

The filter whose transmission is shown in FIG. 20 can be used to shiftthe color temperature of the two Nichia LEDs. The filtered ((1521) and(1531)) and un-filtered ((1201) and (1301)) spectrums for the bin A andC LEDs are shown in FIGS. 21 a and 21 b.

The addition of the yellow filter shifts the color temperature of thebin A LED from 20,000K to 4745K. Its chromaticity coordinates areshifted from (0.27, 0.24) to (0.35, 0.37). The bin C LED is shifted from5750K to 3935K and from chromaticity coordinates (0.33, 0.33) to (0.40,0.43).

The importance of the chromaticity coordinates becomes evident when thecolors of these sources are compared on the CIE 1931 Chromaticity Map.FIG. 22 is a close-up of the chromaticity map around the Plankian locus(1601). This locus indicates the perceived colors of ideal sourcescalled blackbodies. The thicker line (1603) highlights the section ofthe locus that corresponds to the range from 2300K to 4100K.

FIG. 22 illustrates how large of a shift can be achieved with a simplehigh-pass filter. By effectively “warming up” the set of Nichia LEDs,they are brought into a chromaticity range that is useful for thespecified color temperature control range and are suitable for oneembodiment of the invention. The original placement was dashed line(1665), while the new color is represented by line (1607) which iswithin the correct region.

In one embodiment, however, a non-linear range of color temperatures maybe generated using more than two LEDs.

The argument could be made that even a linear variation closelyapproximating the desired range would suffice. This realization wouldcall for an LED close to 2300K and an LED close to 4500K, however. Thiscould be achieved two ways. One, a different LED could be used that hasa color temperature of 2300K. Two, the output of the Nichia bin C LEDcould be passed through an additional filter to shift it even closer tothe 2300K point. Each of these systems comprises an additionalembodiment of the instant invention. However, the following example usesa third LED to meet the desired criteria.

This LED should have a chromaticity to the right of the 2300K point onthe blackbody locus. The Agilent HLMP-EL1 8 amber LED, with a dominantwavelength of 592 nm, has chromaticity coordinates (0.60, 0.40). Theaddition of the Agilent amber to the set of Nichia white LEDs results inthe range (1701) shown in FIG. 23.

The range (1701) produced using these three LEDs completely encompassesthe is blackbody locus over the range from 2300K to 4500K. A lightfixture fabricated using these LEDs may meet the requirement ofproducing white light with the correct chromaticity values. The spectraof the light at 2300K (2203) and 5000K (2201) in FIGS. 26 a and 26 bshow spectra which meet the desired criteria for high-quality whitelight; both spectra are continuous and the 5000K spectrum does not showthe peaks present in other lighting fixtures, with reasonable intensityat all wavelengths. The 2300K spectrum does not have any valleys atlower wavelengths than it's maximum peak. The light is also controllableover these spectra. However, to be considered high-quality white lightby the lighting community, the CRI should be above 50 for low colortemperatures and above 80 for high color temperatures. According to thesoftware program that accompanies the CIE 13.3-1995 specification, theCRI for the 2300K simulated spectrum is 52 and is similar to anincandescent bulb with a CRI of 50. The CRI for the 4500K simulatedspectrum is 82 and is considered to be high-quality white light. Thesespectra are also similar in shape to the spectra of natural light asshown in FIGS. 26 a and 26 b.

FIG. 24 shows the CRI plotted with respect to the CCT for the abovewhite light source. This comparison shows that the high-quality whitelight fixture above will produce white light that is of higher qualitythan the three standard fluorescent lights (1803), (1805), and (1809)used in FIG. 24. Further, the light source above is significantly morecontrollable than a fluorescent light as the color temperature can beselected as any of those points on curve (1801) while the fluorescentsare limited to the particular points shown. The luminous output of thedescribed white light lighting fixture was also measured. The luminousoutput plotted with respect to the color temperature is given in FIG.25, although the graph in FIG. 25 is reliant on the types and levels ofpower used in producing it, the ratio may remain constant with therelative number of the different outer LEDs selected. The full-on point(point of maximum intensity) may be moved by altering the color of eachof the LEDs present.

It would be understood by one of skill in the art that the aboveembodiments of white-light fixtures and methods could also include LEDsor other component illumination sources which produce light not visibleto the human eye. Therefore any of the above embodiments could alsoinclude illumination sources with a maximum spectral peak below 400 nmor above 700 nm.

A high-quality LED-based light may be configured to replace afluorescent tube. In one embodiment, a replacement high-quality LEDlight source useful for replacing fluorescent tubes would function in anexisting device designed to use fluorescent tubes. Such a device isshown in FIG. 28. FIG. 28 shows a typical fluorescent lighting fixtureor other device configured to accept fluorescent tubes (2404). Thelighting fixture (2402) may include a ballast (2410). The ballast (2410)maybe a magnetic type or electronic type ballast for supplying the powerto at least one tube (2404) which has traditionally been a fluorescenttube. The ballast (2410) includes power input connections (2414) to beconnected with an external power supply. The external power supply maybe a building's AC supply or any other power supply known in the art.The ballast (2410) has tube connections (2412) and (2416) which attachto a tube coupler (2408) for easy insertion and removal of tubes (2404).These connections deliver the requisite power to the tube. In a magneticballasted system, the ballast (2410) may be a transformer with apredetermined impedance to supply the requisite voltage and current. Thefluorescent tube (2404) acts like a short circuit so the ballast'simpedance is used to set the tube current. This means that each tubewattage requires a particular ballast. For example, a forty-wattfluorescent tube will only operate on a forty-watt ballast because theballast is matched to the tube. Other fluorescent lighting fixtures useelectronic ballasts with a high frequency sine wave output to the bulb.Even in these systems, the internal ballast impedance of the electronicballast still regulates the current through the tube.

FIG. 29 shows one embodiment of a lighting fixture according to thisdisclosure which could be used as a replacement fluorescent tube in ahousing such as the one in FIG. 28. The lighting fixture may comprise,in one embodiment, a variation on the fighting fixture (5000) in FIGS. 5a and 5 b. The lighting fixture can comprise a bottom portion (1101)with a generally rounded underside (1103) and a generally flatconnection surface (1105). The lighting fixture also comprises a topportion (1111) with a generally rounded upper portion (1113) and agenerally flat connection surface (1115). The top portion (1111) willgenerally be comprised of a translucent, transparent, or similarmaterial allowing light transmission and may comprise a filter similarto filter (391). The flat connection surfaces (1105) and (1115) can beplaced together to form a generally cylindrical lighting fixture and canbe attached by any method known in the art. Between top portion (1111)and bottom portion (1101) is a lighting fixture (1150) which comprises agenerally rectangular mounting (1153) and a strip of at least onecomponent illumination source such as an LED (1155). This constructionis by no means necessary and the lighting fixture need not have ahousing with it or could have a housing of any type known in the art.Although a single strip is shown, one of skill in the art wouldunderstand that multiple strips, or other patterns of arrangement of theillumination sources, could be used. The strips generally have thecomponent LEDs in a sequence that separates the colors of LEDs if thereare multiple colors of LEDs but such an arrangement is not required. Thelighting fixture will generally have lamp connectors (2504) forconnecting the lighting fixture to the existing lamp couplers (2408)(e.g., as shown in FIG. 28). The LED system may also include a controlcircuit (2510). This circuit may convert the ballast voltage into D.C.for the LED operation. The control circuit (2510) may control the LEDs(1155) with constant D.C. voltage or control circuit (2510) may generatecontrol signals to operate the LEDs. In a preferred embodiment, thecontrol circuit (2510) would include a processor for generating pulsewidth modulated control signals, or other similar control signals, forthe LEDs.

These white lights therefore are examples of how a high-quality whitelight fixture can be generated with component illumination sources, evenwhere those sources have dominant wavelengths outside the region of 530nm to 570 nm.

The above white light fixtures can contain programming which enables auser to easily control the light and select any desired colortemperature that is available in the light. In one embodiment, theability to select color temperature can be encompassed in a computerprogram using, for example, the following mathematical equations:Intensity of Amber LED(T)=(5.6×10⁻⁸)T ³−(6.4×10⁻⁴)T ²+(2.3)T−2503.7;Intensity of Warm Nichia LED(T)=(9.5×10⁻³)T ³−(1.2×10⁻³)T²+(4.4)T−5215.2;Intensity of Cool Nichia LED(T)=(4.7×10⁻⁸)T ³−(6.3×10⁻⁴)T²+(2.8)T−3909.6,where T=Temperature in degrees K.

These equations may be applied directly or may be used to create alook-up table so that binary values corresponding to a particular colortemperature can be determined quickly. This table can reside in any formof programmable memory for use in controlling color temperature (suchas, but not limited to, the control described in U.S. Pat. No.6,016,038). In another embodiment, the light could have a selection ofswitches, such as DIP switches enabling it to operate in a stand-alonemode, where a desired color temperature can be selected using theswitches, and changed by alteration of the stand alone product The lightcould also be remotely programmed to operate in a standalone mode asdiscussed above.

The lighting fixture in FIG. 29 may also comprise a program controlswitch (2512). This switch may be a selector switch for selecting thecolor temperature, color of the LED system, or any other illuminationconditions. For example, the switch may have multiple settings fordifferent colors. Position “one” may cause the LED system to produce3200K white light, position “two” may cause 4000K white light, position“three” may be for blue light and a fourth position may be to allow thesystem to receive external signals for color or other illuminationcontrol. This external control could be provided by any of thecontrollers discussed previously.

Some fluorescent ballasts also provide for dimming where a dimmer switchon the wall will change the ballast output characteristics and as aresult change the fluorescent light illumination characteristics. TheLED lighting system may use this as information to change theillumination characteristics. The control circuit (2510) can monitor theballast characteristics and adjust the LED control signals in acorresponding fashion. The LED system may have lighting control signalsstored in memory within the LED lighting system. These control signalsmay be preprogrammed to provide dimming, color changing, a combinationof effects or any other illumination effects as the ballasts'characteristics change.

A user may desire different colors in a room at different times. The LEDsystem can be programmed to produce white light when the dimmer is atthe maximum level, blue light when it is at 90% of maximum, red lightwhen it is at 80%, flashing effects at 70% or continually changingeffects as the dimmer is changed. The system could change color or otherlighting conditions with respect to the dimmer or any other input. Auser may also want to recreate the lighting conditions of incandescentlight. One of the characteristics of such lighting is that it changescolor temperature as its power is reduced. The incandescent light may be2800K at full power but the color temperature will reduce as the poweris reduced and it may be 1500K when the lamp is dimmed to a greatextent. Fluorescent lamps do not reduce in color temperature when theyare dimmed. Typically, the fluorescent lamp's color does not change whenthe power is reduced. The LED system can be programmed to reduce incolor temperature as the lighting conditions are dimmed. This may beachieved using a look-up table for selected intensities, through amathematical description of the relationship between intensity and colortemperature, any other method known in the art, or any combination ofmethods. The LED system can be programmed to provide virtually anylighting conditions.

The LED system may include a receiver for receiving signals, atransducer, a sensor or other device for receiving information. Thereceiver could be any receiver such as, but not limited to, a wire,cable, network, electromagnetic receiver, IR receiver, RF receiver,microwave receiver or any other receiver. A remote control device couldbe provided to change the lighting conditions remotely. Lightinginstructions may also be received from a network. For example, abuilding may have a network where information is transmitted through awireless system and the network could control the illuminationconditions throughout a building. This could be accomplished from aremote site as well as on site. This may provide for added buildingsecurity or energy savings or convenience.

The LED lighting system may also include optics to provide for evenlydistributed lighting conditions from the fluorescent lighting fixture.The optics may be attached to the LED system or associated with thesystem.

The system has applications in environments where variations inavailable lighting may affect aesthetic choices.

In an example embodiment, the lighting fixture may be used in a retailembodiment to sell paint or other color sensitive items. A paint samplemay be viewed in a retail store under the same lighting conditionspresent where the paint will ultimately be used. For example, thelighting fixture may be adjusted for outdoor lighting, or may be morefinely tuned for sunny conditions, cloudy conditions, or the like. Thelighting fixture may also be adjusted for different forms of interiorlighting, such as halogen, fluorescent, or incandescent lighting. In afurther embodiment, a portable sensor (as discussed above) may be takento a site where the paint is to be applied, and the light spectrum maybe analyzed and recorded. The same light spectrum may subsequently bereproduced by the lighting fixture, so that paint may be viewed underthe same lighting conditions present at the site where the paint is tobe used.

The lighting fixture may similarly be used for clothing decisions, wherethe appearance of a particular type and color of fabric may be stronglyinfluenced by lighting conditions. For example, a wedding dress (andbride) may be viewed under lighting conditions expected at a weddingceremony, in order to avoid any unpleasant surprises. The lightingfixture can also be used in any of the applications, or in conjunctionwith any of the systems or methods discussed elsewhere in thisdisclosure.

In another example embodiment, the lighting fixture may be used toaccurately reproduce visual effects. In certain visual arts, such asphotography, cinematography, or theater, make-up is typically applied ina dressing room or a salon, where lighting may be different than on astage or other site. The lighting fixture may thus be used to reproducethe lighting expected where photographs will be taken, or a performancegiven, so that suitable make-up may be chosen for predictable results.As with the retail applications above, a sensor may be used to measureactual lighting conditions so that the lighting conditions may bereproduced during application of make-up.

In theatrical or film presentations, colored light often corresponds tothe colors of specific filters which can be placed on white lightinginstruments to generate a specific resulting shade. There are generallya large selection of such filters in specific shades sold by selectedcompanies. These filters are often classified by a spectrum of theresulting light, by proprietary numerical classifications, and/or bynames which give an implication of the resulting light such as “primaryblue,” “straw,” or “chocolate.” These filters allow for selection of aparticular, reproducible color of light, but, at the same time, limitthe director to those colors of filters that are available. In addition,mixing the colors is not an exact science which can result in, slightvariations in the colors as lighting fixtures are moved, or even changetemperature, during a performance or film shoot. Thus, in one embodimentthere is provided a system for controlling illumination in a theatricalenvironment. In another embodiment, there is provided a system forcontrolling illumination in cinematography.

The wide variety of light sources available create significant problemsfor film production in particular. Differences in lighting betweenadjacent scenes can disrupt the continuity of a film and create jarringeffects for the viewer. Correcting the lighting to overcome thesedifferences can be exacting, because the lighting available in anenvironment is not always under the complete control of the film crew.Sunlight, for example, varies in color temperature during the day, mostapparently at dawn and dusk, when yellows and reds abound, lowering thecolor temperature of the ambient light. Fluorescent light does notgenerally fall on the color temperature curve, often having extraintensity in blue-green regions of the spectrum, and is thus describedby a correlated color temperature, representing the point on the colortemperature curve that best approximates the incident light. Each ofthese lighting problems may be addressed using the systems describedabove.

The availability of a number of different fluorescent bulb types, eachproviding a different color temperature through the use of a particularphosphor, makes color temperature prediction and adjustment even morecomplicated. High-pressure sodium vapor lamps, used primarily for streetlighting, produce a brilliant yellowish-orange light that willdrastically skew color balance. Operating at even higher internalpressures are mercury vapor lamps, sometimes used for large interiorareas such as gymnasiums. These can result in a pronounced greenish-bluecast in video and film. Thus, there is provided a system for simulatingmercury vapor lamps, and a system for supplementing light sources, suchas mercury vapor lamps, to produce a desired resulting color. Theseembodiments may have particular use in cinematography.

To try and recreate all of these lighting types, it is often necessaryfor a filmmaker or theatre designer to place these specific types oflights in their design. At the same time, the need to use these lightsmay thwart the director's theatric intention. The gym lights flashingquickly on and off in a supernatural thriller is a startling-effect, butit cannot be achieved naturally through mercury vapor lamps which takeup to five minutes to warm up and produce the appropriate color light.

Other visually sensitive fields depend on light of a specific colortemperature or spectrum. For example, surgical and dental workers oftenrequire colored light that emphasizes contrasts between differenttissues, as well as between healthy and diseased tissue. Doctors alsooften rely on tracers or markers that reflect, radiate, or fluorescecolor of a specific wavelength or spectrum to enable them to detectblood vessels or other small structures. They can view these structuresby shining light of the specific wavelength in the general area wherethe tracers are, and view the resultant reflection or fluorescing of thetracers. In many instances, different procedures may benefit from usinga customized color temperature or particular color of light tailored tothe needs of each specific procedure. Thus, there is provided a systemfor the visualization of medical, dental or other imaging conditions. Inone embodiment, the system uses LEDs to produce a controlled range oflight within a predetermined spectrum.

Further, there is often a desire to alter lighting conditions during anactivity, a stage should change colors as the sun is supposed to rise, acolor change may occur to change the color of a fluorescing tracer, or aroom could have the color slowly altered to make a visitor moreuncomfortable with the lighting as the length of their stay increased.

While the invention has been disclosed in connection with theembodiments shown and described in detail, various equivalents,modifications, and improvements will be apparent to one of ordinaryskill in the art from the above description. Such equivalents,modifications, and improvements are intended to be encompassed by thefollowing claims.

1. A lighting fixture for producing a beam of light having a luminousflux spectrum emulating that of a beam of light produced by apredetermined light source having an incandescent lamp, such lightsource being free of a filter that modifies the luminous flux spectrumof the light emitted by the lamp, the lighting fixture comprising: aplurality of groups of light-emitting devices, each such groupconfigured to emit light having a distinct luminous flux spectrum; and acontroller configurable to supply selected amounts of electrical powerto the plurality of groups of light-emitting devices, such that thegroups cooperate to produce a composite beam of light having aprescribed luminous flux spectrum that has a normalized mean deviationacross the visible spectrum of less than about 30% relative to theluminous flux spectrum of a beam of light produced by the predeterminedlight source to be emulated.
 2. A lighting fixture as defined in claim1, wherein the quantities of devices included in each of the pluralityof groups of light-emitting devices are selected such that, if thecontroller supplies maximum electrical power to all of the groups, thenthe resulting composite beam of light will have a luminous flux spectrumhaving a normalized mean deviation across the visible spectrum of lessthan about 30% relative to the luminous flux spectrum of a beam of lightproduced by the predetermined light source to be emulated.
 3. A lightingfixture as defined in claim 1, wherein the quantities of devicesincluded in each of the plurality of groups of light-emitting devicesare selected such that, if the controller supplies maximum electricalpower to all of the groups, then the resulting composite beam of lightwill have a luminous flux spectrum having a normalized mean deviationacross the visible spectrum of less than about 30% relative to theluminous flux spectrum of a theoretical beam of light produced by apredetermined light source having an incandescent lamp, as modified by atheoretical superposition of the spectral transmissions of a pluralityof color filters.
 4. A lighting fixture as defined in claim 1 whereinthe controller further is configurable to supply selected amounts ofelectrical power to the plurality of groups of light-emitting devices,such that the groups cooperate to produce a composite beam of lighthaving a prescribed luminous flux spectrum that has a normalized meandeviation across the visible spectrum of less than about 30% relative tothe luminous flux spectrum of a beam of light produced by apredetermined light source that includes an incandescent lamp and afilter that modifies the luminous flux spectrum of the light emitted bysuch lamp.
 5. A lighting fixture as defined in claim 1, wherein at leasttwo of the plurality of groups of light-emitting devices includedifferent quantifies of light-emitting devices.
 6. A lighting fixture asdefined in claim 1, wherein the plurality of groups of light-emittingdevices include at least five groups of light-emitting devices, eachsuch group being configured to emit light having a predetermineddistinct luminous flux spectrum.
 7. A lighting fixture as defined inclaim 1, wherein the plurality of groups of light-emitting devicesinclude at least eight groups of light-emitting devices, each such groupbeing configured to emit light having a predetermined distinct luminousflux spectrum.
 8. A lighting fixture as defined in claim 1, wherein eachof the plurality of groups of light-emitting devices includes aplurality of light-emitting diodes.
 9. A lighting fixture as defined inclaim 1, wherein the plurality of groups of light-emitting devicestogether comprise an optical assembly that collects the emitted lightand projects the composite beam of light from the fixture.
 10. Alighting fixture as defined in claim 1, wherein the luminous fluxspectrum of the composite beam of light has a normalized mean deviationacross the visible spectrum of less than about 25% relative to theluminous flux spectrum of a beam of light produced by the predeterminedlight source to be emulated.
 11. A lighting fixture as defined in claim1, wherein the luminous flux spectrum of the composite beam of light hasa normalized mean deviation across the visible spectrum of less thanabout 20% relative to the luminous flux spectrum of a beam of lightproduced by the predetermined light source to be emulated.
 12. Alighting fixture as defined in claim 1, wherein the luminous fluxspectra of the beam of light produced by the lighting fixture and of thebeam of light produced by the predetermined light source to be emulatedare within 5 db of each other across the visible spectrum when thecontroller supplies prescribed maximum amounts of electrical power toall of the groups of light-emitting devices.
 13. A lighting fixture asdefined in claim 1, wherein the predetermined distinct luminous fluxspectrum of the light emitted by each of the plurality of groups oflight-emitting devices has a spectral half-width of less than about 40nanometers.
 14. A lighting fixture as defined in claim 1, wherein: thedistinct luminous flux spectrum of the light emitted by each of theplurality of groups of light-emitting devices has a predetermined peakflux wavelength and a predetermined spectral half-width; the peak fluxwavelength of each of the plurality of groups of light-emitting devicesis spaced less than about 50 nanometers from the peak flux wavelength ofanother of the plurality of groups of light-emitting devices; and thespectral half-width of each of the plurality of groups of light-emittingdevices is less than about 40 nanometers.
 15. A lighting fixture forproducing a beam of colored light having a prescribed luminous fluxspectrum, the lighting fixture comprising: a plurality of groups oflight-emitting devices, each such group configured to emit light havinga distinct luminous flux spectrum; and a controller configurable tosupply selected amounts of electrical power to the plurality of groupsof light-emitting devices, such that the groups cooperate to produce acomposite beam of light; wherein the composite beam of light has aprescribed luminous flux spectrum having substantial energy only withina contiguous bandwidth of less than about 200 nanometers when thecontroller supplies prescribed maximum amounts of electrical power toall of the groups of light-emitting devices.
 16. A lighting fixture asdefined in claim 15, wherein: each group of light-emitting devices isfree of a filter that substantially changes the luminous flux spectrumof its emitted light; and the controller is configurable to supplyselected amounts of electrical power to the plurality of groups oflight-emitting devices, such that the composite beam of light has aprescribed luminous flux spectrum emulating that of a predeterminedlight source having an incandescent lamp, such light source furtherhaving an associated filter that modifies the luminous flux spectrum ofthe light emitted by the lamp.
 17. A lighting fixture as defined inclaim 16, wherein the luminous flux spectrum of the composite beam oflight has a normalized mean deviation across the visible spectrum ofless than about 30% relative to the luminous flux spectrum of a beam oflight produced by the predetermined light source to be emulated.
 18. Alighting fixture as defined in claim 16, wherein the quantities ofdevices included in each of the plurality of groups of light-emittingdevices are selected such that, if the controller supplies maximumelectrical power to all of the groups, then the resulting composite beamof light will have a luminous flux spectrum having a normalized meandeviation across the visible spectrum of less than about 30% relative tothe luminous flux spectrum of a theoretical beam of light produced bythe predetermined light source, as modified by a theoreticalsuperposition of the spectral transmissions of a plurality of colorfilters.
 19. A lighting fixture as defined in claim 15, wherein thecomposite beam of light produced by the plurality of groups oflight-emitting devices has a luminous flux spectrum having substantialenergy only in wavelengths of less than about 600 nanometers when thecontroller supplies prescribed maximum amounts of electrical power toall of the groups of light-emitting devices.
 20. A lighting fixture asdefined in claim 15, wherein the composite beam of light produced by theplurality of groups of light-emitting devices has a luminous fluxspectrum having substantial energy only in wavelengths of more thanabout 550 nanometers when the controller supplies prescribed maximumamounts of electrical power to all of the groups of light-emittingdevices.
 21. A lighting fixture as defined in claim 15, wherein at leasttwo of the plurality of groups of light-emitting devices includedifferent quantities of light-emitting devices.
 22. A lighting fixtureas defined in claim 15, wherein the plurality of groups oflight-emitting devices include at least four groups of light-emittingdevices, each such group being configured to emit light having apredetermined distinct luminous flux spectrum.
 23. A lighting fixture asdefined in claim 15, wherein each of the plurality of groups oflight-emitting devices includes a plurality of light-emitting diodes.24. A lighting fixture as defined in claim 15, wherein: the distinctluminous flux spectrum of the light emitted by each of the plurality ofgroups of light-emitting devices has a predetermined peak fluxwavelength and a predetermined spectral half-width; the peak fluxwavelength of each of the plurality of groups of light-emitting devicesis spaced less than about 50 nanometers from the peak flux wavelength ofanother of the plurality of groups of light-emitting devices; and thespectral half-width of each of the plurality of groups of light-emittingdevices is less than about 40 nanometers.
 25. A lighting fixture asdefined in claim 15, wherein the composite beam of light has a luminousflux spectrum having substantial energy only within a contiguousbandwidth of less than about 150 nanometers.
 26. A lighting fixture asdefined in claim 15, wherein no portion of the contiguous flux spectrumof the composite beam of light has a flux intensity more than 5 db lowerthan flux intensities at wavelengths both above and below it.
 27. Alighting fixture as defined in claim 15, wherein no portion of thecontiguous flux spectrum of the composite beam of light has a fluxintensity more than 2 db lower than flux intensities at wavelengths bothabove and below it.
 28. A lighting fixture for producing a beam of lighthaving a prescribed luminous flux spectrum, the lighting fixturecomprising: a plurality of groups of light-emitting devices, each suchgroup configured to emit light having a distinct luminous flux spectrum,and at least two of the plurality of groups including differentquantities of devices; and a controller configurable to supply selectedamounts of electrical power to the plurality of groups of light-emittingdevices, such that the groups cooperate to produce a composite beam oflight having a prescribed luminous flux spectrum.
 29. A lighting fixtureas defined in claim 28, wherein: each of the plurality of groups oflight-emitting devices is free of a filter that substantially changesthe luminous flux spectrum of its emitted light; the prescribed luminousflux spectrum is made to emulate that of a beam of light produced by apredetermined light source having an incandescent lamp, such lightsource being free of a filter that modifies the luminous flux spectrumof the light emitted by the lamp; and the controller is configurable tosupply selected amounts of electrical power to the plurality of groupsof light-emitting devices, such that the composite beam of light has aprescribed luminous flux spectrum that has a normalized mean deviationacross the visible spectrum of less than about 30% relative to theluminous flux spectrum of a beam of light produced by the predeterminedlight source to be emulated.
 30. A lighting fixture as defined in claim29, wherein the quantities of devices included in each of the pluralityof groups of light-emitting devices are selected such that, if thecontroller supplies maximum electrical power to all of the groups, thenthe resulting composite beam of light will have a luminous flux spectrumhaving a normalized mean deviation across the visible spectrum of lessthan about 30% relative to the luminous flux spectrum of a beam of lightproduced by the predetermined light source to be emulated.
 31. Alighting fixture as defined in claim 29, wherein the luminous fluxspectra of the beam of light produced by the lighting fixture and of thebeam of light produced by the light source to be emulated are within 5db of each other across the visible spectrum when the controllersupplies prescribed maximum amounts of electrical power to all of thegroups of light-emitting devices.
 32. A lighting fixture as defined inclaim 28, wherein: each group of light-emitting devices is free of afilter that substantially changes the luminous flux spectrum of itsemitted light; the prescribed luminous flux spectrum is made to emulatethat of a beam of light produced by a predetermined light source havingan incandescent lamp, such light source further having an associatedfilter that modifies the luminous flux spectrum of the light emitted bythe lamp; and the controller is configurable to supply selected amountsof electrical power to at least two of the plurality of groups oflight-emitting devices, such that the composite beam of light has aprescribed luminous flux spectrum that has a normalized mean deviationacross the visible spectrum of less than about 30% relative to theluminous flux spectrum of a beam of light produced by the predeterminedlight source to be emulated.
 33. A lighting fixture as defined in claim28, wherein the plurality of groups of light-emitting devices include atleast four groups of light-emitting devices, each such group beingconfigured to emit light having a predetermined distinct luminous fluxspectrum.
 34. A lighting fixture as defined in claim 28, wherein each ofthe plurality of groups of light-emitting devices includes a pluralityof light-emitting diodes.
 35. A lighting fixture as defined in claim 28,wherein: the distinct luminous flux spectrum of the light emitted byeach of the plurality of groups of light-emitting devices has apredetermined peak flux wavelength and a predetermined spectralhalf-width; the peak flux wavelength of each of the plurality of groupsof light-emitting devices is spaced less than about 50 nanometers fromthe peak flux wavelength of another of the plurality of groups oflight-emitting devices; and the spectral half-width of each of theplurality of groups of light-emitting devices is less than about 40nanometers.
 36. A lighting fixture for producing a beam of light havinga prescribed luminous flux spectrum, the lighting fixture comprising:five or more groups of light-emitting devices, wherein each such groupis configured to emit light having a distinct luminous flux spectrum;and a controller configurable to supply selected amounts of electricalpower to the five or more groups of light-emitting devices, such thatthe groups cooperate to produce a composite beam of light having aprescribed luminous flux spectrum.
 37. A lighting fixture as defined inclaim 36, wherein the five or groups of light-emitting devices includeat least eight groups of light-emitting devices, each such group beingconfigured to emit light having a predetermined distinct luminous fluxspectrum.
 38. A lighting fixture as defined in claim 36, wherein each ofthe five or more groups of light-emitting devices includes a pluralityof light-emitting diodes.
 39. A lighting fixture as defined in claim 36,wherein: the distinct luminous flux spectrum of the light emitted byeach of the five or more groups of light-emitting devices has apredetermined peak flux wavelength and a predetermined spectralhalf-width; the peak flux wavelength of each of the plurality of groupsof light-emitting devices is spaced less than about 50 nanometers fromthe peak flux wavelength of another of the plurality of groups oflight-emitting devices; and the spectral half-width of each of theplurality of groups of light-emitting devices is less than about 40nanometers.
 40. A lighting fixture as defined in claim 36, wherein thefive or more groups of light-emitting devices cooperate to emit lightspanning substantially the entire visible spectrum.
 41. A lightingfixture for producing a beam of light having a prescribed luminous fluxspectrum, the lighting fixture comprising: three or more groups oflight-emitting devices, each such group configured to emit light havinga distinct luminous flux spectrum with a predetermined peak fluxwavelength and a predetermined spectral half-width; wherein the peakflux wavelength of each of the four or more groups of light-emittingdevices is spaced less than about 50 nanometers from the peak fluxwavelength of another of the groups of light-emitting devices; andwherein the spectral half-width of each of the four or more groups oflight-emitting devices is less than about 40 nanometers; and acontroller configurable to supply selected amounts of electrical powerto the four or more groups of light-emitting devices, such that thegroups cooperate to produce a composite beam of light having aprescribed luminous flux spectrum.
 42. A lighting fixture as defined inclaim 41, wherein the three or more groups of light-emitting devicesinclude eight or more groups of light-emitting devices, each such groupconfigured to emit light having a distinct luminous flux spectrum with apredetermined peak flux wavelength and a predetermined spectralhalf-width.
 43. A lighting fixture as defined in claim 41, wherein: eachof the plurality of groups of light-emitting devices is free of a filterthat substantially changes the luminous flux spectrum of its emittedlight; the prescribed luminous flux spectrum is made to emulate that ofa beam of light produced by a predetermined light source having anincandescent lamp, such light source being free of a filter thatmodifies the luminous flux spectrum of the light emitted by the lamp;and the controller is configurable to supply selected amounts ofelectrical power to the plurality of groups of light-emitting devices,such that the composite beam of light has a prescribed luminous fluxspectrum that has a normalized mean deviation across the visiblespectrum of less than about 30% relative to the luminous flux spectrumof a beam of light produced by the predetermined light source to beemulated.